autofs: update ioctl documentation regarding struct autofs_dev_ioctl

				 * including this struct */

	__s32 ioctlfd;          /* automount command fd */

	/* Command parameters */

	union {

		struct args_protover		protover;

		struct args_protosubver		protosubver;

                                         * including this struct */

                __s32 ioctlfd;          /* automount command fd */

                __u32 arg1;             /* Command parameters */

                __u32 arg2;

		/* Command parameters */

		union {

			struct args_protover		protover;

			struct args_protosubver		protosubver;

			struct args_openmount		openmount;

			struct args_ready		ready;

			struct args_fail		fail;

			struct args_setpipefd		setpipefd;

			struct args_timeout		timeout;

			struct args_requester		requester;

			struct args_expire		expire;

			struct args_askumount		askumount;

			struct args_ismountpoint	ismountpoint;

		};

                char path[0];

        };

    set version numbers.

- **AUTOFS_DEV_IOCTL_OPENMOUNT_CMD**: return an open file descriptor

    on the root of an autofs filesystem.  The filesystem is identified

    by name and device number, which is stored in `arg1`.  Device

    numbers for existing filesystems can be found in

    by name and device number, which is stored in `openmount.devid`.

    Device numbers for existing filesystems can be found in

    `/proc/self/mountinfo`.

- **AUTOFS_DEV_IOCTL_CLOSEMOUNT_CMD**: same as `close(ioctlfd)`.

- **AUTOFS_DEV_IOCTL_SETPIPEFD_CMD**: if the filesystem is in

    catatonic mode, this can provide the write end of a new pipe

    in `arg1` to re-establish communication with a daemon.  The

    process group of the calling process is used to identify the

    in `setpipefd.pipefd` to re-establish communication with a daemon.

    The process group of the calling process is used to identify the

    daemon.

- **AUTOFS_DEV_IOCTL_REQUESTER_CMD**: `path` should be a

    name within the filesystem that has been auto-mounted on.

    On successful return, `arg1` and `arg2` will be the UID and GID

    of the process which triggered that mount.

    On successful return, `requester.uid` and `requester.gid` will be

    the UID and GID of the process which triggered that mount.

- **AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD**: Check if path is a

    mountpoint of a particular type - see separate documentation for

    details.

- **AUTOFS_DEV_IOCTL_PROTOVER_CMD**:

- **AUTOFS_DEV_IOCTL_PROTOSUBVER_CMD**:

- **AUTOFS_DEV_IOCTL_READY_CMD**:

- **AUTOFS_DEV_IOCTL_EXPIRE_CMD**:

- **AUTOFS_DEV_IOCTL_ASKUMOUNT_CMD**:  These all have the same

    function as the similarly named **AUTOFS_IOC** ioctls, except

    that **FAIL** can be given an explicit error number in `arg1`

    that **FAIL** can be given an explicit error number in `fail.status`

    instead of assuming `ENOENT`, and this **EXPIRE** command

    corresponds to **AUTOFS_IOC_EXPIRE_MULTI**.