t/zbd: Do not use too large block size in test case #4

t/zbd: Do not use too large block size in test case #4

The test case #4 specifies zone size as block size to read a zone. For
some devices, zone size is very large in GB order, then single pread64
system call can not complete the request. This makes the test case fail.

To avoid the failure, keep the block size adequate. If zone size is too
large, use logical_block_size * 256 as the block size.

Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Reviewed-by: Niklas Cassel <niklas.cassel@wdc.com>
Link: https://lore.kernel.org/r/20211013060903.166543-4-shinichiro.kawasaki@wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>