Rename TEXT_BASE into CONFIG_SYS_TEXT_BASE

The change is currently needed to be able to remove the board
configuration scripting from the top level Makefile and replace it by
a simple, table driven script.

Moving this configuration setting into the "CONFIG_*" name space is
also desirable because it is needed if we ever should move forward to
a Kconfig driven configuration system.

Signed-off-by: Wolfgang Denk <wd@denx.de>
diff --git a/board/siemens/SMN42/lowlevel_init.S b/board/siemens/SMN42/lowlevel_init.S
index f13d9b9..44e209b 100644
--- a/board/siemens/SMN42/lowlevel_init.S
+++ b/board/siemens/SMN42/lowlevel_init.S
@@ -38,7 +38,7 @@
 #define   IO0_VALUE   0x4000C
 
 _TEXT_BASE:
-	.word	TEXT_BASE
+	.word	CONFIG_SYS_TEXT_BASE
 MEMMAP_ADR:
 	.word	MEMMAP
 BCFG0_ADR: