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/board/openpiton/riscv64/Kconfig b/board/openpiton/riscv64/Kconfig
index 193c890..eb0db8a 100644
--- a/board/openpiton/riscv64/Kconfig
+++ b/board/openpiton/riscv64/Kconfig
@@ -12,7 +12,7 @@
 config SYS_CONFIG_NAME
 	default "openpiton-riscv64"
 
-config SYS_TEXT_BASE
+config TEXT_BASE
 	default 0x81000000 if SPL
 	default 0x80000000 if !RISCV_SMODE
 	default 0x81000000 if RISCV_SMODE