Makefile: remove tx25 exception

An entry in the main Makefile for the tx25 board is not
necessary, and the board is added to boards.cfg as all
other targets.
Signed-off-by: NStefano Babic <sbabic@denx.de>
CC: Wolfgang Denk <wd@denx.de>

Makefile

@@ -866,10 +866,6 @@ SX1_config:		unconfig
 	fi;
 	@$(MKCONFIG) -n $@ SX1 arm arm925t sx1
 
-tx25_config	: unconfig
-	@echo "CONFIG_NAND_U_BOOT = y" >> $(obj)include/config.mk
-	@$(MKCONFIG) $@ arm arm926ejs tx25 karo mx25
-
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 ## XScale Systems
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