comedi: convert sysfs snprintf 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: Xuezhi Zhang <zhangxuezhi1@coolpad.com>
Link: https://lore.kernel.org/r/20220901013423.418464-1-zhangxuezhi3@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>