Previous commit added support for sum 'compression' (rather
postprocessing) of jffs2 images. Drop support for sum.jffs2 image type.
(From OE-Core rev: 295c6c1452c8789a8b1d0090ff09a5cd7cf16507)
Signed-off-by: Dmitry Eremin-Solenikov <dmitry_eremin@mentor.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>