Add LZO1X compression/decompression support to jffs2.

LZO's interface doesn't entirely match that required by jffs2 so a
buffer and memcpy is unavoidable.
Signed-off-by: NRichard Purdie <rpurdie@openedhand.com>
Signed-off-by: NDavid Woodhouse <dwmw2@infradead.org>