paride/pd: remove ->revalidate_disk

->revalidate_disk is only called during add_disk for pd, but at that
point the driver has already set the capacity to the one returned from
Identify a little earlier, so this additional update is entirely
superflous.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210308074550.422714-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>