Resending the patch. Addressed the review comments from Tomas Henzl.
Reduce the assingment for u64 req_data variable.

Use writeq() for 64bit PCI write instead of writel() to avoid additional lock overhead.
Signed-off-by: NSumit Saxena <sumit.saxena@avagotech.com>
Signed-off-by: NKashyap Desai <kashyap.desai@avagotech.com>
Reviewed-by: NTomas Henzl <thenzl@redhat.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>