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/imx8qxp_mek_defconfig b/configs/imx8qxp_mek_defconfig
index 73600c5..3865eb3 100644
--- a/configs/imx8qxp_mek_defconfig
+++ b/configs/imx8qxp_mek_defconfig
@@ -1,6 +1,6 @@
 CONFIG_ARM=y
 CONFIG_ARCH_IMX8=y
-CONFIG_SYS_TEXT_BASE=0x80020000
+CONFIG_TEXT_BASE=0x80020000
 CONFIG_SYS_MALLOC_LEN=0x2400000
 CONFIG_SYS_MALLOC_F_LEN=0x4000
 CONFIG_SPL_GPIO=y