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/stv0991_defconfig b/configs/stv0991_defconfig
index f2e8677..750437b 100644
--- a/configs/stv0991_defconfig
+++ b/configs/stv0991_defconfig
@@ -1,7 +1,7 @@
 CONFIG_ARM=y
 CONFIG_SYS_DCACHE_OFF=y
 CONFIG_TARGET_STV0991=y
-CONFIG_SYS_TEXT_BASE=0x00010000
+CONFIG_TEXT_BASE=0x00010000
 CONFIG_SYS_MALLOC_LEN=0x14000
 CONFIG_NR_DRAM_BANKS=1
 CONFIG_ENV_SIZE=0x10000