vhost-scsi: convert sysfs snprintf and sprintf to sysfs_emit

Follow the advice of the Documentation/filesystems/sysfs.rst
and show() should only use sysfs_emit() or sysfs_emit_at()
when formatting the value to be returned to user space.

Signed-off-by: Bo Liu <liubo03@inspur.com>
Message-Id: <20230129091145.2837-1-liubo03@inspur.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>