Makefile: Fix mvebu build target to use SPL load and exe-address

The u-boot-spl.kwb build target needs the SPL text-base
(CONFIG_SPL_TEXT_BASE) as load and execution address.
Signed-off-by: NStefan Roese <sr@denx.de>

Makefile

@@ -887,7 +887,7 @@ MKIMAGEFLAGS_u-boot.kwb = -n $(srctree)/$(CONFIG_SYS_KWD_CONFIG:"%"=%) \
 	-T kwbimage -a $(CONFIG_SYS_TEXT_BASE) -e $(CONFIG_SYS_TEXT_BASE)
 
 MKIMAGEFLAGS_u-boot-spl.kwb = -n $(srctree)/$(CONFIG_SYS_KWD_CONFIG:"%"=%) \
-	-T kwbimage -a $(CONFIG_SYS_TEXT_BASE) -e $(CONFIG_SYS_TEXT_BASE)
+	-T kwbimage -a $(CONFIG_SPL_TEXT_BASE) -e $(CONFIG_SPL_TEXT_BASE)
 
 MKIMAGEFLAGS_u-boot.pbl = -n $(srctree)/$(CONFIG_SYS_FSL_PBL_RCW:"%"=%) \
 		-R $(srctree)/$(CONFIG_SYS_FSL_PBL_PBI:"%"=%) -T pblimage