cdrom: docs: reformat table in Documentation/userspace-api/ioctl/cdrom.rst

Add extra space to the first column of ioctl values table, and also realign
the text in the second column, to fix a documentation build warning
introduced by: commit 67f1e027 ("drivers/cdrom: improved ioctl for
media change detection")

Suggested-by: Randy Dunlap <rdunlap@infradead.org>
Fixes: 67f1e027 ("drivers/cdrom: improved ioctl for media change detection")
Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20211007231720.31997-1-phil@philpotter.co.uk


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