mm/oom-kill: Allow __GFP_RETRY_MAYFAIL to fail fast

This flag indicates that the memory request may fail, if
the system is low on memory. The caller is prepared to handle
this scenario.

Change-Id: Ie4be1f3048196a38946d08f7355e2673e097018c
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>