loop: remove the unused inode variable in loop_configure

Remove the inode variable now that the last user is gone.

Fixes: a17ece76 ("loop: regularize upgrading the block size for direct I/O")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20240705053114.2042976-1-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>