mm: treat indirectly reclaimable memory as available in MemAvailable

Adjust /proc/meminfo MemAvailable calculation by adding the amount of
indirectly reclaimable memory (rounded to the PAGE_SIZE).

This change is referenced from commit 034ebf65c3c2 ("mm: treat indirectly
reclaimable memory as available in MemAvailable") on upstream, as node
based vmstat global_node_page_state is not present, zone based vmstat
global_page_state is used instead.

Change-Id: I7303d0f8ccd5993c7234a5187430d418d49e5763
Signed-off-by: Vijayanand Jitta <vjitta@codeaurora.org>