Revert "mm: oom-kill: Add lmk_kill possible for ULMK"

This reverts commit de771054.

The effectiveness of should_ulmk_retry() is being re-assessed - for the
time being, we'll let the OOM killer run, when an allocation in alloc_pages
fails.

Change-Id: Ife3af938fc356ce46f8d9c538aaf6bd5d0c404f8
Signed-off-by: Chris Goldsworthy <cgoldswo@codeaurora.org>