PM / devfreq: memlat: fix suspend/resume calls to devfreq_monitor

The memlat governor suspend/resume callbacks always call devfreq_monitor
suspend/resume functions. The devfreq_monitor suspend/resume functions
run with the assumption that we had started devfreq->work and do a sync
wait to cancel it. However, when should_ignore_df_monitor flag is set,
memlat relies on its own workqueue and devfreq->work is never started.
Cancelling a timer that was never started leads to a crash. Fix this by
only calling devfreq_monitor suspend/resume functions when the
should_ignore_df_monitor flag is not set.

Change-Id: Ie4aff96b6b845f4f5424652943405a572b91b8ca
Signed-off-by: Amir Vajid <avajid@codeaurora.org>