subsys/audio: sof: use mem_slab for buffers

Zephyr's k_mem_pool does not allocate buffers that are cache line
and/or DMA transfers aligned. The manual cache line manipulations
has the potential to disrupt the k_mem_pool's own tracking
information, and thus causing exceptions in freeing the memory.
So the memory allocator is modified to use memory slab for
buffers, and it needs to be initialized.

Shrink the size of k_mem_pool as buffers are not being allocated
from there.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>

Author: dcpleung

samples/audio/sof/prj.conf

@@ -4,4 +4,4 @@ CONFIG_LOG_PRINTK=y
 CONFIG_LOG_IMMEDIATE=y
 CONFIG_SOF_LOG_LEVEL=4
 # SOF requires malloc/calloc
-CONFIG_HEAP_MEM_POOL_SIZE=196608
+CONFIG_HEAP_MEM_POOL_SIZE=65536

subsys/audio/sof.c

@@ -17,6 +17,7 @@ LOG_MODULE_REGISTER(sof, CONFIG_SOF_LOG_LEVEL);
 #include <platform/dma.h>
 #include <platform/shim.h>
 #include <platform/timer.h>
+#include <sof/alloc.h>
 #include <sof/clk.h>
 #include <sof/interrupt.h>
 #include <sof/mailbox.h>
@@ -290,6 +291,8 @@ static int sof_init(struct device *unused)
 {
 	int ret;
 
+	malloc_init();
+
 	platform_interrupt_init();
 
 	/* prepare host windows */