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/davinci/da8xxevm/README.da850 b/board/davinci/da8xxevm/README.da850
index 8cebdcc..50ef401 100644
--- a/board/davinci/da8xxevm/README.da850
+++ b/board/davinci/da8xxevm/README.da850
@@ -124,7 +124,7 @@
 u-boot.bin is directy flashed, but CONFIT_DA850_LOWLEVEL must be set
 to initialize hardware that's normally done by SPL.
 
-For this case, CONFIG_SYS_TEXT_BASE=0x60000000 which is the address to
+For this case, CONFIG_TEXT_BASE=0x60000000 which is the address to
 which the bootloader jumps when powered on.
 
 Example: