autofs: add command enum/macros for root-dir ioctls

Sync root-dir ioctl with misc-char-dev ioctl's enum/macro format since
these two types of ioctls aren't completely independent of each other in
terms of command nr.  No functional changes.

Link: http://lkml.kernel.org/r/148577166143.9801.15511796506678428145.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>