drm/radeon: clean reg header files

Reg header files are generated so they are not cleaned automagically.
They need to be added to the clean-files list.
Signed-off-by: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/Makefile

@@ -5,6 +5,7 @@
 ccflags-y := -Iinclude/drm
 
 hostprogs-y := mkregtable
+clean-files := rn50_reg_safe.h r100_reg_safe.h r200_reg_safe.h rv515_reg_safe.h r300_reg_safe.h r420_reg_safe.h rs600_reg_safe.h r600_reg_safe.h evergreen_reg_safe.h cayman_reg_safe.h
 
 quiet_cmd_mkregtable = MKREGTABLE $@
       cmd_mkregtable = $(obj)/mkregtable $< > $@