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/Kconfig b/arch/arm/Kconfig
index 8bc9aaf..710f171 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -93,7 +93,7 @@
 	depends on LINUX_KERNEL_IMAGE_HEADER
 	hex
 	help
-	  The value subtracted from CONFIG_SYS_TEXT_BASE to calculate the
+	  The value subtracted from CONFIG_TEXT_BASE to calculate the
 	  TEXT_OFFSET value written to the Linux kernel image header.
 
 config GICV2