ARM: make memset and memcpy prompt message more clearly

The origin SPL_USE_ARCH_MEMSET/MEMCPY use same prompt message
as USE_ARCH_MEMSET/MEMCPY, which makes it's hard to distinguish
them in menuconfig interface. This patch gives them different
prompt messages for spl and none-spl config.

Signed-off-by: Andy Yan <andy.yan@rock-chips.com>

arch/arm/Kconfig

@@ -253,7 +253,7 @@ config USE_ARCH_MEMCPY
 	  but may increase the binary size.
 
 config SPL_USE_ARCH_MEMCPY
-	bool "Use an assembly optimized implementation of memcpy"
+	bool "Use an assembly optimized implementation of memcpy for SPL"
 	default y if USE_ARCH_MEMCPY
 	depends on !ARM64
 	help
@@ -271,7 +271,7 @@ config USE_ARCH_MEMSET
 	  but may increase the binary size.
 
 config SPL_USE_ARCH_MEMSET
-	bool "Use an assembly optimized implementation of memset"
+	bool "Use an assembly optimized implementation of memset for SPL"
 	default y if USE_ARCH_MEMSET
 	depends on !ARM64
 	help