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/doc/README.ARM-memory-map b/doc/README.ARM-memory-map
index e2c4e16..1b120ac 100644
--- a/doc/README.ARM-memory-map
+++ b/doc/README.ARM-memory-map
@@ -9,8 +9,8 @@
 >
 >How are they (should they be) set in your memory map above?
 
-_armboot_start contains the value of TEXT_BASE (0xA07E0000); it seems
-TEXT_BASE and _armboot_start are both used for the same purpose in
+_armboot_start contains the value of CONFIG_SYS_TEXT_BASE (0xA07E0000); it seems
+CONFIG_SYS_TEXT_BASE and _armboot_start are both used for the same purpose in
 different parts of the (ARM) code.
 Furthermore, the startup code (cpu/<arm>/start.S) internally uses
 another variable (_TEXT_BASE) with the same content as _armboot_start.