lib: fix compilation error with gcc++

The header files including must be outside of the extern "C" { statement.
To be able to be included from C++ code.

Else such error can occur (reproduce on STM32MP1Cube distribution)
gcc/arm-none-eabi/include/c++/10.2.1/atomic:1467:3: error: template
with C linkage
 1467 |   template<typename _ITp>
      |   ^~~~~~~~
In file included from STM32CubeMP1/Middlewares/Third_Party/OpenAMP/
                      open-amp/lib/include/openamp/rpmsg.h:16,
                 from STM32CubeMP1/Middlewares/Third_Party/OpenAMP/
                      open-amp/lib/include/openamp/open_amp.h:11,
                 from empty_main.cpp:1:
STM32CubeMP1/Middlewares/Third_Party/OpenAMP/libmetal/lib/include/
metal/mutex.h:16:1: note: 'extern "C"' linkage
started here
   16 | extern "C" {
      | ^~~~~~~~~~

Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>

lib/alloc.h

@@ -36,12 +36,12 @@ static inline void *metal_allocate_memory(unsigned int size);
  */
 static inline void metal_free_memory(void *ptr);
 
-#include <metal/system/@PROJECT_SYSTEM@/alloc.h>
-
 /** @} */
 
 #ifdef __cplusplus
 }
 #endif
 
+#include <metal/system/@PROJECT_SYSTEM@/alloc.h>
+
 #endif /* __METAL_ALLOC__H__ */

lib/condition.h

@@ -63,12 +63,12 @@ static inline int metal_condition_broadcast(struct metal_condition *cv);
  */
 int metal_condition_wait(struct metal_condition *cv, metal_mutex_t *m);
 
-#include <metal/system/@PROJECT_SYSTEM@/condition.h>
-
 /** @} */
 
 #ifdef __cplusplus
 }
 #endif
 
+#include <metal/system/@PROJECT_SYSTEM@/condition.h>
+
 #endif /* __METAL_CONDITION__H__ */

lib/dma.h

@@ -12,6 +12,9 @@
 #ifndef __METAL_DMA__H__
 #define __METAL_DMA__H__
 
+#include <stdint.h>
+#include <metal/sys.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -20,9 +23,6 @@ extern "C" {
  *  @{
  */
 
-#include <stdint.h>
-#include <metal/sys.h>
-
 #define METAL_DMA_DEV_R  1 /**< DMA direction, device read */
 #define METAL_DMA_DEV_W  2 /**< DMA direction, device write */
 #define METAL_DMA_DEV_WR 3 /**< DMA direction, device read/write */

lib/io.h

@@ -363,12 +363,12 @@ int metal_io_block_write(struct metal_io_region *io, unsigned long offset,
 int metal_io_block_set(struct metal_io_region *io, unsigned long offset,
 		       unsigned char value, int len);
 
-#include <metal/system/@PROJECT_SYSTEM@/io.h>
-
 /** @} */
 
 #ifdef __cplusplus
 }
 #endif
 
+#include <metal/system/@PROJECT_SYSTEM@/io.h>
+
 #endif /* __METAL_IO__H__ */

lib/irq.h

@@ -12,6 +12,9 @@
 #ifndef __METAL_IRQ__H__
 #define __METAL_IRQ__H__
 
+#include <metal/list.h>
+#include <stdlib.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -20,9 +23,6 @@ extern "C" {
  *  @{
  */
 
-#include <metal/list.h>
-#include <stdlib.h>
-
 /** IRQ handled status */
 #define METAL_IRQ_NOT_HANDLED 0
 #define METAL_IRQ_HANDLED     1

lib/mutex.h

@@ -12,6 +12,8 @@
 #ifndef __METAL_MUTEX__H__
 #define __METAL_MUTEX__H__
 
+#include <metal/system/@PROJECT_SYSTEM@/mutex.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -20,8 +22,6 @@ extern "C" {
  *  @{
  */
 
-#include <metal/system/@PROJECT_SYSTEM@/mutex.h>
-
 /**
  * @brief	Initialize a libmetal mutex.
  * @param[in]	mutex	Mutex to initialize.

lib/softirq.h

@@ -12,6 +12,8 @@
 #ifndef __METAL_SOFTIRQ__H__
 #define __METAL_SOFTIRQ__H__
 
+#include <metal/irq.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -20,8 +22,6 @@ extern "C" {
  *  @{
  */
 
-#include <metal/irq.h>
-
 /**
  * @brief	metal_softirq_init
  *

lib/time.h

@@ -12,6 +12,9 @@
 #ifndef __METAL_TIME__H__
 #define __METAL_TIME__H__
 
+#include <stdint.h>
+#include <metal/sys.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -20,9 +23,6 @@ extern "C" {
  *  @{
  */
 
-#include <stdint.h>
-#include <metal/sys.h>
-
 /**
  * @brief      get timestamp
  *             This function returns the timestampe as unsigned long long