Merge branch 'for-3.16/core' into for-3.16/drivers

Pull in core changes (again), since we got rid of the alloc/free
hctx mq_ops hooks and mtip32xx then needed updating again.

Signed-off-by: Jens Axboe <axboe@fb.com>

diff --cc drivers/block/mtip32xx/mtip32xx.c
Simple merge

diff --cc drivers/block/null_blk.c
Simple merge

diff --cc drivers/block/virtio_blk.c
Simple merge