If rootmode isn't valid, we hit the BUG() in fuse_init_inode.  Now
EINVAL is returned.
Signed-off-by: NTimo Savola <tsavola@movial.fi>
Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>