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/stm32f746-disco_spl_defconfig b/configs/stm32f746-disco_spl_defconfig
index e9b0f82..2c58aef 100644
--- a/configs/stm32f746-disco_spl_defconfig
+++ b/configs/stm32f746-disco_spl_defconfig
@@ -1,6 +1,6 @@
 CONFIG_ARM=y
 CONFIG_ARCH_STM32=y
-CONFIG_SYS_TEXT_BASE=0x08009000
+CONFIG_TEXT_BASE=0x08009000
 CONFIG_SYS_MALLOC_LEN=0x100000
 CONFIG_SPL_GPIO=y
 CONFIG_SPL_LIBCOMMON_SUPPORT=y