This patch moves the NVMe driver from drivers/block/ to its own new
drivers/nvme/host/ directory. This is in preparation of splitting the
current monolithic driver up and add support for the upcoming NVMe
over Fabrics standard. The drivers/nvme/host/ is chose to leave space
for a NVMe target implementation in addition to this host side driver.

Signed-off-by: Jay Sternberg
[hch: rebased, renamed core.c to pci.c, slight tweaks]
Signed-off-by: Christoph Hellwig
Acked-by: Keith Busch
Signed-off-by: Jens Axboe