[JFFS2] Prevent list corruption when handling write errors

If a write error occurs, the affected block is placed on the
bad_used_list.  In the case that the write error occured
when writing summary data the block was also being placed on
the dirty_list, which caused list corruption and ultimately
a soft lockup in jffs2_mark_node_obsolete. This fixes that.

Signed-off-by: Adrian Hunter <ext-adrian.hunter@nokia.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>