Implement ->map queues and use the block layer blk_mq_pci_map_queues
helper for mapping queues to CPUs.

With this mapping minimum 10%+ increase in performance is noticed.
Signed-off-by: Saurav Kashyap <skashyap@marvell.com>
Signed-off-by: Nilesh Javali <njavali@marvell.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>