mm: show_free_areas(): display slab pages in two separate fields

If an OOM happens, we really want to know the number of remaining
reclaimable pages.  So the reclaimable slab and unreclaimable slab fields
should not be combined for display.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>