t/zbd: fix minimum write size to sequential write required zones

t/zbd: fix minimum write size to sequential write required zones

ZBC and ZAC require that writes to sequential write required zones shall
be aligned to physical block size. However, the t/zbd/test-zbd-support
script uses logical block size as the minimum write size. When SMR
drives have the physical block size larger than the logical block size,
writes with the logical block size causes unaligned write command error.

To fix it, use correct value as the minimum write size. As for zoned
block devices, introduce a helper function min_seq_write_size(), which
checks sysfs attributes and returns the correct size. Refer the
attribute zone_write_granularity when it is available, which provides the
minimum write size regardless of the device type. If the attribute is
not available, refer the attribute physical_block_size for SMR devices,
and the logical_block_size attribute for other devices. As for SG node
device, refer physical block size that zbc_info command reports.

Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Signed-off-by: Vincent Fu <vincent.fu@samsung.com>