[JFFS2] Fix summary handling of unknown but compatible nodes.

For RWCOMPAT and ROCOMPAT nodes, we should still allow the mount to
succeed. Just abandon the summary and fall through to the full scan.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

diff --cc fs/jffs2/erase.c
Simple merge

diff --cc fs/jffs2/nodelist.h
Simple merge

diff --cc fs/jffs2/summary.c
Simple merge