mm: oom_kill: Prevent debug messages from going to serial console

Some devices use a watchdog driver which requires each cpu to be able to
handle an IPI within one second. Since printing to serial console disables
interrupts, the large amount of messages generated by dump_tasks() may
trigger this scenario. Therefore, ensure that these messages are
not displayed in nonfatal scenarios.

Also fix a logic error with strcmp.

Change-Id: Ifb6a09431747431478ce26ff89e38d6c6724af2d
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>