android/lowmemorykiller: Account for total_swapcache_pages

The lowmemorykiller relies on NR_FILE_PAGES when measureing
the amount of reclaimable memory in the system.
However when swap is enabled swap cache pages are counted
in NR_FILE_PAGES, and swap cache pages aren't as reclaimable
in low memory as file cache pages. Therefore a large swap
cache can result in the lowmemorykiller not running and
an OOM occuring.

In order to ensure the lowmemorykiller properly evaluates the
amount of reclaimable memory don't count the swap cache pages.

Signed-off-by: Liam Mark <lmark@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>

Conflicts:
	drivers/staging/android/lowmemorykiller.c
LMK tweaks
Revert "random: check for increase of entropy_count because of signed conversion"

This reverts commit db1e01ddf0c7da3140ae46863c37ea12b85c6fa0.
Revert "random: fix nasty entropy accounting bug"

This reverts commit 81993e63b7f326d5e7069371327103df8622e0e1.