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/Kconfig b/drivers/Kconfig
index 46b4a8e..e69ec82a 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -18,6 +18,8 @@
 
 source "drivers/block/Kconfig"
 
+source "drivers/nvme/Kconfig"
+
 # misc before ide - BLK_DEV_SGIIOC4 depends on SGI_IOC4
 
 source "drivers/misc/Kconfig"