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/configs/stemmy_defconfig b/configs/stemmy_defconfig
index 90f2970..ff9667a 100644
--- a/configs/stemmy_defconfig
+++ b/configs/stemmy_defconfig
@@ -5,7 +5,7 @@
 CONFIG_SUPPORT_PASSING_ATAGS=y
 # CONFIG_SETUP_MEMORY_TAGS is not set
 CONFIG_INITRD_TAG=y
-CONFIG_SYS_TEXT_BASE=0x100000
+CONFIG_TEXT_BASE=0x100000
 CONFIG_SYS_MALLOC_LEN=0x0200000
 CONFIG_SYS_MALLOC_F_LEN=0x400
 CONFIG_NR_DRAM_BANKS=2