nvme: move to a new drivers/nvme/host directory

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 <jay.e.sternberg@intel.com>
[hch: rebased, renamed core.c to pci.c, slight tweaks]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/drivers/Makefile b/drivers/Makefile
index b250b36..42f9dd5 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -70,6 +70,7 @@
 obj-y				+= macintosh/
 obj-$(CONFIG_IDE)		+= ide/
 obj-$(CONFIG_SCSI)		+= scsi/
+obj-y				+= nvme/
 obj-$(CONFIG_ATA)		+= ata/
 obj-$(CONFIG_TARGET_CORE)	+= target/
 obj-$(CONFIG_MTD)		+= mtd/