block: blk_max_size_offset() should check ->max_sectors

Commit 762380ad9322 inadvertently changed a check for max_sectors
to max_hw_sectors. Revert that part, so we still compare against
max_sectors.

Signed-off-by: Jens Axboe <axboe@fb.com>

diff --cc include/linux/blkdev.h
Simple merge