zbd: Fix partition block device handling

zbd: Fix partition block device handling

For fio to correctly handle the zonemode=zbd mode with partitions of
zoned block devices, the partition block device file must be identified
as a zoned disk. However, partition block device files do not have
a zoned sysfs file. This patch allows a correct identification of the
device file zone model by accessing the sysfs "zoned" file of the
holder disk for partition devices.

Change get_zbd_model() function to resolve the symbolic link to the
sysfs path to obtain the canonical sysfs path. The canonical sysfs
path of a partition device includes both of the holder device name and
the partition device name. If the given device is a partition device,
cut the partition device name in the canonical sysfs path to access
the "zoned" file in the holder device sysfs path.

Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>