fuse: don't use inode in fuse_sync_release()

Make fuse_sync_release() a generic helper function that doesn't need a
struct inode pointer.  This makes it suitable for use by CUSE.

Change return value of fuse_release_common() from int to void.

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