fuse: don't use inode in helpers called by fuse_direct_io()

Use ff->fc and ff->nodeid instead of passing down the 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/dir.c
Simple merge

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

diff --cc fs/fuse/fuse_i.h
Simple merge