blk-mq-dma: fix kernel-doc function name for integrity DMA iterator

blk-mq-dma: fix kernel-doc function name for integrity DMA iterator

Documentation build reported:

  Warning: block/blk-mq-dma.c:373 expecting prototype for blk_rq_integrity_dma_map_iter_start(). Prototype was for blk_rq_integrity_dma_map_iter_next() instead

The kernel-doc comment above `blk_rq_integrity_dma_map_iter_next()` used
the wrong function name (`blk_rq_integrity_dma_map_iter_start`) in its
header. This patch corrects the function name in the kernel-doc block to
match the actual implementation, ensuring clean documentation builds.

Fixes: fec9b16dc555 ("blk-mq-dma: add scatter-less integrity data DMA mapping")
Signed-off-by: Kriish Sharma <kriish.sharma2006@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>