CMSIS5: Remove ARM7 support and targets

Author: bulislaw

platform/mbed_retarget.cpp

@@ -766,9 +766,6 @@ extern "C" uint32_t  __HeapLimit;
 #undef errno
 extern "C" int errno;
 
-// For ARM7 only
-register unsigned char * stack_ptr __asm ("sp");
-
 // Dynamic memory allocation related syscall.
 #if defined(TARGET_NUMAKER_PFM_NUC472) || defined(TARGET_NUMAKER_PFM_M453)
 // Overwrite _sbrk() to support two region model (heap and stack are two distinct regions).
@@ -785,9 +782,7 @@ extern "C" caddr_t _sbrk(int incr) {
     unsigned char*        prev_heap = heap;
     unsigned char*        new_heap = heap + incr;
 
-#if defined(TARGET_ARM7)
-    if (new_heap >= stack_ptr) {
-#elif defined(TARGET_CORTEX_A)
+#if defined(TARGET_CORTEX_A)
     if (new_heap >= (unsigned char*)&__HeapLimit) {     /* __HeapLimit is end of heap section */
 #else
     if (new_heap >= (unsigned char*)__get_MSP()) {