HAL: Rename platform init function

Align with HAL design document:
 - Rename 'tfm_spm_hal_post_init' to 'tfm_hal_platform_init'.
 - Set 'tfm_hal_platform_init' to weak, and platform with specific init
   operation needs to override it.
 - Remove 'tfm_spm_hal_post_init_platform' and move the operations to
   'tfm_hal_platform_init'.

Change-Id: Ia96b3a6bae716d154edab8709eb6e277bafcb45e
Signed-off-by: Summer Qin <summer.qin@arm.com>
diff --git a/platform/ext/common/tfm_platform.c b/platform/ext/common/tfm_platform.c
index fc9ecb7..fd13dc2 100644
--- a/platform/ext/common/tfm_platform.c
+++ b/platform/ext/common/tfm_platform.c
@@ -8,23 +8,14 @@
 #include "target_cfg.h"
 #include "tfm_spm_hal.h"
 #include "uart_stdout.h"
+#include "tfm_hal_platform.h"
 
-/* platform-specific hw initialization */
-__WEAK enum tfm_plat_err_t tfm_spm_hal_post_init_platform(void)
+__WEAK enum tfm_hal_status_t tfm_hal_platform_init(void)
 {
-    return TFM_PLAT_ERR_SUCCESS;
-}
-
-enum tfm_plat_err_t tfm_spm_hal_post_init(void)
-{
-    if (tfm_spm_hal_post_init_platform() != TFM_PLAT_ERR_SUCCESS) {
-        return TFM_PLAT_ERR_SYSTEM_ERR;
-    }
-
     __enable_irq();
     stdio_init();
 
-    return TFM_PLAT_ERR_SUCCESS;
+    return TFM_HAL_SUCCESS;
 }
 
 __WEAK void tfm_hal_system_reset(void)