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/silk_defconfig b/configs/silk_defconfig
index 8498500..38a1476 100644
--- a/configs/silk_defconfig
+++ b/configs/silk_defconfig
@@ -4,7 +4,7 @@
 # CONFIG_SPL_USE_ARCH_MEMCPY is not set
 # CONFIG_SPL_USE_ARCH_MEMSET is not set
 CONFIG_ARCH_RMOBILE=y
-CONFIG_SYS_TEXT_BASE=0x50000000
+CONFIG_TEXT_BASE=0x50000000
 CONFIG_SYS_MALLOC_LEN=0x100000
 CONFIG_SYS_MALLOC_F_LEN=0x8000
 CONFIG_SPL_LIBCOMMON_SUPPORT=y