sr: set GENHD_FL_REMOVABLE earlier

Set up GENHD_FL_REMOVABLE together with the rest of the gendisk fields.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211122130625.1136848-15-hch@lst.de


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