scsi: sd: Align maximum write same blocks to physical block size

Reporting a maximum number of blocks that is not aligned on the device
physical size would cause a large write same request to be split into
physically unaligned chunks by __blkdev_issue_write_zeroes() and
__blkdev_issue_write_same(), even if the caller of these functions took
care to align its request to physical sectors.

Make sure the maximum reported is aligned to the device physical block
size. This is only an optional optimization for regular disks, but this
is mandatory to avoid failure of large write same requests directed at
sequential write required zones of host-managed ZBC disks.

[mkp: tweaked commit message]

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Bart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>