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/MPC8548CDS_36BIT_defconfig b/configs/MPC8548CDS_36BIT_defconfig
index 50bc6d6..3833596 100644
--- a/configs/MPC8548CDS_36BIT_defconfig
+++ b/configs/MPC8548CDS_36BIT_defconfig
@@ -1,6 +1,6 @@
 CONFIG_PPC=y
 CONFIG_SYS_IMMR=0xE0000000
-CONFIG_SYS_TEXT_BASE=0xFFF80000
+CONFIG_TEXT_BASE=0xFFF80000
 CONFIG_SYS_MALLOC_LEN=0x100000
 CONFIG_ENV_SIZE=0x2000
 CONFIG_ENV_SECT_SIZE=0x20000