services/spm_deprecated: update ARM platform specific asserts

Update some asserts that refer to #defines that only occur in
ARM platforms, preventing this code to be used on other platforms.
Instead, use a platform agnostic name, and update all the existing
users.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
diff --git a/plat/arm/board/fvp/fvp_common.c b/plat/arm/board/fvp/fvp_common.c
index 31a61de..fa5539d 100644
--- a/plat/arm/board/fvp/fvp_common.c
+++ b/plat/arm/board/fvp/fvp_common.c
@@ -218,12 +218,12 @@
 	.sp_image_base       = ARM_SP_IMAGE_BASE,
 	.sp_stack_base       = PLAT_SP_IMAGE_STACK_BASE,
 	.sp_heap_base        = ARM_SP_IMAGE_HEAP_BASE,
-	.sp_ns_comm_buf_base = ARM_SP_IMAGE_NS_BUF_BASE,
+	.sp_ns_comm_buf_base = PLAT_SP_IMAGE_NS_BUF_BASE,
 	.sp_shared_buf_base  = PLAT_SPM_BUF_BASE,
 	.sp_image_size       = ARM_SP_IMAGE_SIZE,
 	.sp_pcpu_stack_size  = PLAT_SP_IMAGE_STACK_PCPU_SIZE,
 	.sp_heap_size        = ARM_SP_IMAGE_HEAP_SIZE,
-	.sp_ns_comm_buf_size = ARM_SP_IMAGE_NS_BUF_SIZE,
+	.sp_ns_comm_buf_size = PLAT_SP_IMAGE_NS_BUF_SIZE,
 	.sp_shared_buf_size  = PLAT_SPM_BUF_SIZE,
 	.num_sp_mem_regions  = ARM_SP_IMAGE_NUM_MEM_REGIONS,
 	.num_cpus            = PLATFORM_CORE_COUNT,
diff --git a/plat/arm/board/fvp/include/platform_def.h b/plat/arm/board/fvp/include/platform_def.h
index ca4bd53..31f06a9 100644
--- a/plat/arm/board/fvp/include/platform_def.h
+++ b/plat/arm/board/fvp/include/platform_def.h
@@ -271,8 +271,8 @@
 #define PLAT_ARM_PRIVATE_SDEI_EVENTS	ARM_SDEI_PRIVATE_EVENTS
 #define PLAT_ARM_SHARED_SDEI_EVENTS	ARM_SDEI_SHARED_EVENTS
 
-#define PLAT_ARM_SP_IMAGE_STACK_BASE	(ARM_SP_IMAGE_NS_BUF_BASE +	\
-					 ARM_SP_IMAGE_NS_BUF_SIZE)
+#define PLAT_ARM_SP_IMAGE_STACK_BASE	(PLAT_SP_IMAGE_NS_BUF_BASE +	\
+					 PLAT_SP_IMAGE_NS_BUF_SIZE)
 
 #define PLAT_SP_PRI			PLAT_RAS_PRI