[PATCH] fix fsync(dir) return value for ram-based filesystems

Any filesystem which is using simple_dir_operations will retunr -EINVAL for
fsync() on a directory.  Make it return zero instead.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>