nvme-fc: create fc class and transport device

Added a new fc class and a device node for udev events under it.  I
expect the fc class will eventually be the location where the FC SCSI and
FC NVME merge in the future. Therefore names are kept somewhat generic.

Signed-off-by: James Smart <james.smart@broadcom.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>