mm: enable nr_indirectly_reclaimable

Display nr_indirectly_reclaimable in /proc/vmstat.
This is useful to account memory in reclaimable pools
like ION which can be of considerable size.

Change-Id: Ic7af97c389bb6a6ef720ce8c4f1169bf1bb959f0
Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>