powerpc/bootwrapper: Pad .dtb by default

Since most bootloaders or wrappers tend to update or add some information
to the .dtb they a handled they need some working space to do that in.

By default add 1K of padding via a default setting of DTS_FLAGS.
Signed-off-by: NKumar Gala <galak@kernel.crashing.org>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

arch/powerpc/boot/Makefile

@@ -35,6 +35,8 @@ endif
 
 BOOTCFLAGS	+= -I$(obj) -I$(srctree)/$(obj) -I$(srctree)/$(src)/libfdt
 
+DTS_FLAGS	?= -p 1024
+
 $(obj)/4xx.o: BOOTCFLAGS += -mcpu=405
 $(obj)/ebony.o: BOOTCFLAGS += -mcpu=405
 $(obj)/cuboot-taishan.o: BOOTCFLAGS += -mcpu=405