block: also return bio_integrity_payload * from stubs

block: also return bio_integrity_payload * from stubs

struct bio_integrity_payload is defined unconditionally. No need to
return void * from bio_integrity() and bio_integrity_alloc().

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Kanchan Joshi <joshi.k@samsung.com>
Reviewed-by: Anuj Gupta <anuj20.g@samsung.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20240702151047.1746127-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>