apm-emulation: use wait_event_freezable() instead of freezer_[do_not_]count()
vfork is moving away from freezer_[do_not_]count() one way or the
other leaving apm_ioctl() as the only user. apm_ioctl() just wants to
wait for suspend/resume cycle to complete without hindering the
freezer. Use wait_event_freezable() instead.
The only annoyance is that wait_event_freezable() wakes up with
-ERESTART if there are pending signals while apm_ioctl() wants to
ignore all signals until suspend is complete. We can play with
@current->[real_]blocked but this is hardly a performance or latency
critical path - simply chill a bit on each iteration until
SUSPEND_DONE for unlikely cases where there are pending signals.