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/arch/mips/mach-mtmips/Kconfig b/arch/mips/mach-mtmips/Kconfig
index d46be50..15b2792 100644
--- a/arch/mips/mach-mtmips/Kconfig
+++ b/arch/mips/mach-mtmips/Kconfig
@@ -28,7 +28,7 @@
 config SYS_SCACHE_LINE_SIZE
 	default 32 if SOC_MT7621
 
-config SYS_TEXT_BASE
+config TEXT_BASE
 	default 0x9c000000 if !SPL && !SOC_MT7621
 	default 0x80200000 if SPL || SOC_MT7621