Rename CONFIG_SYS_TEXT_BASE to CONFIG_TEXT_BASE

The current name is inconsistent with SPL which uses CONFIG_SPL_TEXT_BASE
and this makes it imposible to use CONFIG_VAL().

Rename it to resolve this problem.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/mach-keystone/config.mk b/arch/arm/mach-keystone/config.mk
index 5a16891..8eccbdb 100644
--- a/arch/arm/mach-keystone/config.mk
+++ b/arch/arm/mach-keystone/config.mk
@@ -27,7 +27,7 @@
 
 ifndef CONFIG_SPL_BUILD
 MKIMAGEFLAGS_MLO = -A $(ARCH) -T gpimage -C none \
-	-a $(CONFIG_SYS_TEXT_BASE) -e $(CONFIG_SYS_TEXT_BASE) -n U-Boot
+	-a $(CONFIG_TEXT_BASE) -e $(CONFIG_TEXT_BASE) -n U-Boot
 MLO: u-boot.bin FORCE
 	$(call if_changed,mkimage)
 	@dd if=/dev/zero bs=8 count=1 2>/dev/null >> $@