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/openpiton_riscv64_defconfig b/configs/openpiton_riscv64_defconfig
index 176b374..04c37f4 100644
--- a/configs/openpiton_riscv64_defconfig
+++ b/configs/openpiton_riscv64_defconfig
@@ -1,5 +1,5 @@
 CONFIG_RISCV=y
-CONFIG_SYS_TEXT_BASE=0x80200000
+CONFIG_TEXT_BASE=0x80200000
 CONFIG_SYS_MALLOC_LEN=0x10000000
 CONFIG_NR_DRAM_BANKS=1
 CONFIG_DEFAULT_DEVICE_TREE="openpiton-riscv64"