skd: Use unified access to skdev->msix_entries throughout the code

Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: linux-pci@vger.kernel.org
Signed-off-by: Jens Axboe <axboe@fb.com>