mm/page_owner.c: clean up init_pages_in_zone()

mm/page_owner.c: clean up init_pages_in_zone()

Remove two redundant assignments in init_pages_in_zone().

[osalvador@techadventures.net: v3]
Link: http://lkml.kernel.org/r/20180117124513.GA876@techadventures.net
[akpm@linux-foundation.org: coding style tweaks]
Link: http://lkml.kernel.org/r/20180110084355.GA22822@techadventures.net
Signed-off-by: Oscar Salvador <osalvador@techadventures.net>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>