autofs: fix wrong ioctl documentation regarding devid

This is the same as d8732841 except that it's a different file.  A
caller has no devid input, and devid is obtained via superblock.

Link: http://lkml.kernel.org/r/148577165119.9801.16967562019122274820.stgit@pluto.themaw.net


Signed-off-by: Tomohiro Kusumi <tkusumi@tuxera.com>
Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>