amiflop: convert to blk-mq

Straightforward conversion, just use the existing amiflop_lock to
serialize access to the controller. Compile-tested only.

Cc: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>

Converted to blk_mq_init_sq_queue()

Signed-off-by: Jens Axboe <axboe@kernel.dk>