ARM: 7152/1: distclean: Remove generated .dtb files

The patch 'arm/dt: Add dtb make rule' adds support to
create a .dtb file. But this is never removed afterwards.
Remove the generated .dtb file if 'distclean' is called.
Signed-off-by: NDirk Behme <dirk.behme@de.bosch.com>
Acked-by: NRob Herring <rob.herring@calxeda.com>
Acked-by: NGrant Likely <grant.likely@secretlab.ca>
Cc: Shawn Guo <shawn.guo@freescale.com>
Cc: Jason Liu <jason.hui@linaro.org>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

arch/arm/boot/Makefile

@@ -65,6 +65,8 @@ $(obj)/%.dtb: $(src)/dts/%.dts
 
 $(obj)/dtbs: $(addprefix $(obj)/, $(dtb-y))
 
+clean-files := *.dtb
+
 quiet_cmd_uimage = UIMAGE  $@
       cmd_uimage = $(CONFIG_SHELL) $(MKIMAGE) -A arm -O linux -T kernel \
 		   -C none -a $(LOADADDR) -e $(STARTADDR) \