Mbed TLS: Remove weak heap implementation

The implementation of the heap function plat_get_mbedtls_heap() becomes
mandatory for platforms supporting TRUSTED_BOARD_BOOT.

The shared Mbed TLS heap default weak function implementation is
converted to a helper function get_mbedtls_heap_helper() which can be
used by the platforms for their own function implementation.

Change-Id: Ic8f2994e25e3d9fcd371a21ac459fdcafe07433e
Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>
diff --git a/include/plat/common/platform.h b/include/plat/common/platform.h
index 4832e49..3f9ab1b 100644
--- a/include/plat/common/platform.h
+++ b/include/plat/common/platform.h
@@ -47,6 +47,7 @@
 uintptr_t plat_get_ns_image_entrypoint(void);
 unsigned int plat_my_core_pos(void);
 int plat_core_pos_by_mpidr(u_register_t mpidr);
+int plat_get_mbedtls_heap(void **heap_addr, size_t *heap_size);
 
 #if STACK_PROTECTOR_ENABLED
 /*
@@ -103,7 +104,6 @@
 const char *plat_log_get_prefix(unsigned int log_level);
 void bl2_plat_preload_setup(void);
 int plat_try_next_boot_source(void);
-int plat_get_mbedtls_heap(void **heap_addr, size_t *heap_size);
 uint64_t *plat_init_apiakey(void);
 
 /*******************************************************************************
@@ -262,6 +262,7 @@
 int plat_set_nv_ctr(void *cookie, unsigned int nv_ctr);
 int plat_set_nv_ctr2(void *cookie, const struct auth_img_desc_s *img_desc,
 		unsigned int nv_ctr);
+int get_mbedtls_heap_helper(void **heap_addr, size_t *heap_size);
 
 /*******************************************************************************
  * Secure Partitions functions