scsi: sd_zbc: Rearrange code

Rearrange sd_zbc_setup() to include use_16_for_rw and use_10_for_rw
assignments and move the calculation of sdkp->zone_shift together with
the assignment of the verified zone_blocks value in
sd_zbc_check_zone_size().

No functional change is introduced by this patch.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <Bart.VanAssche@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>