Several functions in this driver are called from atomic context,
and thus raw locks must be used in order to be safe on PREEMPT_RT.

This includes paths that must wait for command completion, which is
a potential PREEMPT_RT latency concern but not easily avoidable.
Signed-off-by: Scott Wood <swood@redhat.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>