JFFS2: memory leak in jffs2_do_mount_fs()

If  jffs2_sum_init()  fails,  c->blocks is not freed neither in
jffs2_do_mount_fs() nor in jffs2_do_fill_super().

Signed-off-by: Dmitry Adamushko <dmitry.adamushko@gmail.com>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>