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/cmc_pu2/config.mk b/board/cmc_pu2/config.mk
index 7116eea..cdb8a5f 100644
--- a/board/cmc_pu2/config.mk
+++ b/board/cmc_pu2/config.mk
@@ -1,3 +1,3 @@
-TEXT_BASE = 0x20F00000
+CONFIG_SYS_TEXT_BASE = 0x20F00000
 ## For testing: load at 0x20100000 and "go" at 0x201000A4
-#TEXT_BASE = 0x20100000
+#CONFIG_SYS_TEXT_BASE = 0x20100000