The unsigned 32 bits overflow check for the zone size value is already
done within sd_zbc_check_zones() with the test:

} else if (logical_to_sectors(sdkp->device, zone_blocks) > UINT_MAX) {

so there is no need to check again for an out of range value in
sd_zbc_read_zones(). Simplify the code and fix sd_zbc_check_zones()
error return to -EFBIG instead of -ENODEV if the zone size is too large.
Change the return type of sd_zbc_check_zones() to an int for the error
code and return the zone size (zone_blocks) through a u32 pointer to
avoid overflowing the signed 32 return value.
Reviewed-by: Hannes Reinecke <hare@suse.com>
Acked-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>