keystone2: Rename local CONFIG_ symbol

CONFIG_SPL_STACK_SIZE is not a config option, so rename it.

Signed-off-by: Phil Edworthy <phil.edworthy@renesas.com>

include/configs/ti_armv7_keystone2.h

@@ -47,11 +47,11 @@
 #define CONFIG_SYS_SPL_MALLOC_START	(CONFIG_SPL_BSS_START_ADDR + \
 					CONFIG_SPL_BSS_MAX_SIZE)
 #define CONFIG_SYS_SPL_MALLOC_SIZE	(32 * 1024)
-#define CONFIG_SPL_STACK_SIZE		(8 * 1024)
+#define KEYSTONE_SPL_STACK_SIZE		(8 * 1024)
 #define CONFIG_SPL_STACK		(CONFIG_SYS_SPL_MALLOC_START + \
 					CONFIG_SYS_SPL_MALLOC_SIZE + \
 					SPL_MALLOC_F_SIZE + \
-					CONFIG_SPL_STACK_SIZE - 4)
+					KEYSTONE_SPL_STACK_SIZE - 4)
 #define CONFIG_SPL_SPI_LOAD
 #define CONFIG_SYS_SPI_U_BOOT_OFFS	CONFIG_SPL_PAD_TO