fuse: don't use inode in fuse_do_ioctl() helper

Create a helper for sending an IOCTL request that doesn't use a struct
inode.

This prepares this function for use by CUSE, where the inode is not
owned by a fuse filesystem.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

diff --cc fs/fuse/file.c
Simple merge