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/arm/cpu/armv8/start.S b/arch/arm/cpu/armv8/start.S
index 28f0df1..f3ea858 100644
--- a/arch/arm/cpu/armv8/start.S
+++ b/arch/arm/cpu/armv8/start.S
@@ -35,7 +35,7 @@
 
 .globl	_TEXT_BASE
 _TEXT_BASE:
-	.quad	CONFIG_SYS_TEXT_BASE
+	.quad	CONFIG_TEXT_BASE
 
 /*
  * These are defined in the linker script.