mon_get_cpu() is indirectly called monitor_parse_arguments() where
the current monitor isn't set yet. Instead of using monitor_cur(),
explicitly pass the Monitor pointer to the function.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20201113114326.97663-2-kwolf@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>