xfs: remove xfs_blkdev_put

There isn't much use for this trivial wrapper, especially as the NULL
check is only needed in a single call site.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Message-Id: <20230809220545.1308228-5-hch@lst.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>