mm, oom: Modify default value of panic_on_oom

If a userspace low memory killer is present, the kernel oom killer
is not expected to be invoked. Therefore, trigger a reset on any
such occurrence.

Change-Id: I7f3451e9c4deb843b3e4dfa13e9764101e90b8ae
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>
Signed-off-by: Chris Goldsworthy <cgoldswo@codeaurora.org>