Convert CFG_SYS_UBOOT_START to Kconfig

Commit 65cc0e2a65d2 ("global: Move remaining CONFIG_SYS_* to CFG_SYS_*")
renamed CONFIG_SYS_UBOOT_START to CFG_SYS_UBOOT_START. Unfortunately,
this meant that the value was no longer available to the Makefile. This
caused imxrt to fail to boot. All the other boards that used this
variable were unaffected because they were using the default value
which is CONFIG_TEXT_BASE.

This commit converts CFG_SYS_UBOOT_START to Kconfig and sets the default
value to CONFIG_TEXT_BASE.

Suggested-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Suggested-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Jesse Taube <Mr.Bossman075@gmail.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/Makefile b/Makefile
index efbaf43..b62f0a6 100644
--- a/Makefile
+++ b/Makefile
@@ -1367,14 +1367,6 @@
 u-boot.ldr.hex u-boot.ldr.srec: u-boot.ldr FORCE
 	$(call if_changed,objcopy)
 
-#
-# U-Boot entry point, needed for booting of full-blown U-Boot
-# from the SPL U-Boot version.
-#
-ifndef CFG_SYS_UBOOT_START
-CFG_SYS_UBOOT_START := $(CONFIG_TEXT_BASE)
-endif
-
 # Boards with more complex image requirements can provide an .its source file
 # or a generator script
 # NOTE: Please do not use this. We are migrating away from Makefile rules to use
@@ -1394,7 +1386,7 @@
 
 ifdef CONFIG_SPL_LOAD_FIT
 MKIMAGEFLAGS_u-boot.img = -f auto -A $(ARCH) -T firmware -C none -O u-boot \
-	-a $(CONFIG_TEXT_BASE) -e $(CFG_SYS_UBOOT_START) \
+	-a $(CONFIG_TEXT_BASE) -e $(CONFIG_SYS_UBOOT_START) \
 	-p $(CONFIG_FIT_EXTERNAL_OFFSET) \
 	-n "U-Boot $(UBOOTRELEASE) for $(BOARD) board" -E \
 	$(patsubst %,-b arch/$(ARCH)/dts/%.dtb,$(subst ",,$(DEVICE_TREE))) \
@@ -1402,10 +1394,10 @@
 	$(patsubst %,-b arch/$(ARCH)/dts/%.dtbo,$(subst ",,$(CONFIG_OF_OVERLAY_LIST)))
 else
 MKIMAGEFLAGS_u-boot.img = -A $(ARCH) -T firmware -C none -O u-boot \
-	-a $(CONFIG_TEXT_BASE) -e $(CFG_SYS_UBOOT_START) \
+	-a $(CONFIG_TEXT_BASE) -e $(CONFIG_SYS_UBOOT_START) \
 	-n "U-Boot $(UBOOTRELEASE) for $(BOARD) board"
 MKIMAGEFLAGS_u-boot-ivt.img = -A $(ARCH) -T firmware_ivt -C none -O u-boot \
-	-a $(CONFIG_TEXT_BASE) -e $(CFG_SYS_UBOOT_START) \
+	-a $(CONFIG_TEXT_BASE) -e $(CONFIG_SYS_UBOOT_START) \
 	-n "U-Boot $(UBOOTRELEASE) for $(BOARD) board"
 u-boot-ivt.img: MKIMAGEOUTPUT = u-boot-ivt.img.log
 endif
@@ -1436,7 +1428,7 @@
 UBOOT_BIN := u-boot.bin
 
 MKIMAGEFLAGS_u-boot-lzma.img = -A $(ARCH) -T standalone -C lzma -O u-boot \
-	-a $(CONFIG_TEXT_BASE) -e $(CFG_SYS_UBOOT_START) \
+	-a $(CONFIG_TEXT_BASE) -e $(CONFIG_SYS_UBOOT_START) \
 	-n "U-Boot $(UBOOTRELEASE) for $(BOARD) board"
 
 u-boot.bin.lzma: u-boot.bin FORCE