Makefile.lib: align DTB quiet_cmd

The unaligned dtb.S filename in make output started to irritate me:
  DTC     arch/metag/boot/dts/skeleton.dtb
  DTB    arch/metag/boot/dts/skeleton.dtb.S
  AS      arch/metag/boot/dts/skeleton.dtb.o
  LD      arch/metag/boot/dts/built-in.o

Add an extra space to quiet_cmd_dt_S_dtb so the dtb.S filename aligns
with all the others.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Dirk Brandewie <dirk.brandewie@gmail.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: trivial@kernel.org
Signed-off-by: Michal Marek <mmarek@suse.cz>

scripts/Makefile.lib

@@ -244,7 +244,7 @@ cmd_gzip = (cat $(filter-out FORCE,$^) | gzip -n -f -9 > $@) || \
 # ---------------------------------------------------------------------------
 
 # Generate an assembly file to wrap the output of the device tree compiler
-quiet_cmd_dt_S_dtb= DTB    $@
+quiet_cmd_dt_S_dtb= DTB     $@
 cmd_dt_S_dtb=						\
 (							\
 	echo '\#include <asm-generic/vmlinux.lds.h>'; 	\