To be able to properly be able to keep references to block queues,
we make blk_init_queue() return the queue that it initialized, and
let it be independently allocated and then cleaned up on the last
reference.

I have grepped high and low, and there really shouldn't be any broken
uses of blk_init_queue() in the kernel drivers left.  The added bonus
being blk_init_queue() error checking is explicit now, most of the
drivers were broken in this regard (even IDE/SCSI).

No drivers have embedded request queue structures. Drivers that don't
use blk_init_queue() but blk_queue_make_request(), should allocate the
queue with blk_alloc_queue(gfp_mask). I've converted all of them to do
that, too. They can call blk_cleanup_queue() now too, using the define
blk_put_queue() is probably cleaner though.