Fix PREEMPTION=y and BLK_CGROUP=y config on arm64

With PREEMPTION=y and BLK_CGROUP=y preempt_schedule_notrace() is being
used on arm64 which is a GPL-only function and hence the build of the
DKMS kernel module fails.

Fix that by redefining preempt_schedule_notrace() to preempt_schedule()
which should be safe as long as tracing is not used.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Closes #8545
Closes #9948
Closes #10416
Closes #10973