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/tplink_wdr4300_defconfig b/configs/tplink_wdr4300_defconfig
index a7faca2..b60f634 100644
--- a/configs/tplink_wdr4300_defconfig
+++ b/configs/tplink_wdr4300_defconfig
@@ -1,5 +1,5 @@
 CONFIG_MIPS=y
-CONFIG_SYS_TEXT_BASE=0xA1000000
+CONFIG_TEXT_BASE=0xA1000000
 CONFIG_SYS_MALLOC_LEN=0x40000
 CONFIG_ENV_SIZE=0x10000
 CONFIG_DEFAULT_DEVICE_TREE="tplink_wdr4300"