nvme: set queue limits for the admin queue

Factor out a helper to set all the device specific queue limits and apply
them to the admin queue in addition to the I/O queues.  Without this the
command size on the admin queue is arbitrarily low, and the missing
other limitations are just minefields waiting for victims.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Jeff Lien <Jeff.Lien@hgst.com>
Tested-by: Jeff Lien <Jeff.Lien@hgst.com>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>