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/board/google/chromebook_samus/Kconfig b/board/google/chromebook_samus/Kconfig
index 9f66d79..011968a 100644
--- a/board/google/chromebook_samus/Kconfig
+++ b/board/google/chromebook_samus/Kconfig
@@ -13,7 +13,7 @@
 	default "chromebook_samus" if TARGET_CHROMEBOOK_SAMUS
 	default "chromebook_samus" if TARGET_CHROMEBOOK_SAMUS_TPL
 
-config SYS_TEXT_BASE
+config TEXT_BASE
 	default 0xffe00000
 
 config BOARD_SPECIFIC_OPTIONS # dummy