arm: remove unneeded symbol offsets and _TEXT_BASE

Remove the last uses of symbol offsets in ARM U-Boot.
Remove some needless uses of _TEXT_BASE.
Remove all _TEXT_BASE definitions.

Signed-off-by: Albert ARIBAUD <albert.u.boot@aribaud.net>
diff --git a/board/cm41xx/flash.c b/board/cm41xx/flash.c
index 2511928..8315a57 100644
--- a/board/cm41xx/flash.c
+++ b/board/cm41xx/flash.c
@@ -57,7 +57,7 @@
 	 */
 	flash_protect (FLAG_PROTECT_SET,
 		       CONFIG_SYS_FLASH_BASE,
-		       CONFIG_SYS_FLASH_BASE + _bss_start_ofs,
+		       CONFIG_SYS_FLASH_BASE + (__bss_end - __bss_start),
 		       &flash_info[0]);
 
 	return size;