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/taurus_defconfig b/configs/taurus_defconfig
index e95ee1b..6fc7199 100644
--- a/configs/taurus_defconfig
+++ b/configs/taurus_defconfig
@@ -8,7 +8,7 @@
 # CONFIG_SPL_USE_ARCH_MEMCPY is not set
 # CONFIG_SPL_USE_ARCH_MEMSET is not set
 CONFIG_ARCH_AT91=y
-CONFIG_SYS_TEXT_BASE=0x21000000
+CONFIG_TEXT_BASE=0x21000000
 CONFIG_SYS_MALLOC_LEN=0x460000
 CONFIG_TARGET_TAURUS=y
 CONFIG_AT91_GPIO_PULLUP=y