block: pass a queue_limits argument to blk_alloc_disk

block: pass a queue_limits argument to blk_alloc_disk

Pass a queue_limits to blk_alloc_disk and apply it if non-NULL.  This
will allow allocating queues with valid queue limits instead of setting
the values one at a time later.

Also change blk_alloc_disk to return an ERR_PTR instead of just NULL
which can't distinguish errors.

Signed-off-by: Christoph Hellwig <hch@lst.de>