MX28: Move the u-boot.bd info CPUDIR/SOCDIR

This gets us rid of duplication of the same file.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Stefano Babic <sbabic@denx.de>
Acked-by: Stefano Babic <sbabic@denx.de>
diff --git a/Makefile b/Makefile
index 42fc5ee..913360c 100644
--- a/Makefile
+++ b/Makefile
@@ -450,7 +450,7 @@
 			$(obj)u-boot.ais
 
 $(obj)u-boot.sb:       $(obj)u-boot.bin $(obj)spl/u-boot-spl.bin
-		elftosb -zdf imx28 -c $(TOPDIR)/board/$(BOARDDIR)/u-boot.bd \
+		elftosb -zdf imx28 -c $(TOPDIR)/$(CPUDIR)/$(SOC)/u-boot.bd \
 			-o $(obj)u-boot.sb
 
 # On x600 (SPEAr600) U-Boot is appended to U-Boot SPL.