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/mx6sllevk_plugin_defconfig b/configs/mx6sllevk_plugin_defconfig
index bd44298..47d8254 100644
--- a/configs/mx6sllevk_plugin_defconfig
+++ b/configs/mx6sllevk_plugin_defconfig
@@ -1,6 +1,6 @@
 CONFIG_ARM=y
 CONFIG_ARCH_MX6=y
-CONFIG_SYS_TEXT_BASE=0x87800000
+CONFIG_TEXT_BASE=0x87800000
 CONFIG_SYS_MALLOC_LEN=0x1000000
 CONFIG_NR_DRAM_BANKS=1
 CONFIG_ENV_SIZE=0x2000