ps3disk: use memcpy_{from,to}_bvec

Use the bvec helpers instead of open coding the copy.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Tested-by: Geoff Levand <geoff@infradead.org>
Link: https://lore.kernel.org/r/20210727055646.118787-9-hch@lst.de


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