block: simplify block device syncing in bdev_del_partition
We just checked a little above that the block device for the partition
im busy. That implies no file system is mounted, and thus the only
thing in fsync_bdev that actually is used is sync_blockdev. Just call
sync_blockdev directly.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>