block: take offset into account in blk_bvec_map_sg again

The rebase of commit 09595e0c ("block: pass a phys_addr_t to
get_max_segment_size") lost adding the total to to the offset in
blk_bvec_map_sg.  Add it back.

Fixes: 09595e0c

 ("block: pass a phys_addr_t to get_max_segment_size")
Reported-by: Yi Zhang <yi.zhang@redhat.com>
Reported-by: Chaitanya Kulkarni <chaitanyak@nvidia.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20240709070126.3019940-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>