machine: add more JFFS2_ERASEBLOCK definitions

some missing found googling on the web
0x40000 explicited even if image_types.bbclass default

Signed-off-by: Andrea Adami <andrea.adami@gmail.com>
zaurus.inc: set default IMAGE_CMD_sum.jffs2 for devices with NAND

Collie will need a customization.

Signed-off-by: Andrea Adami <andrea.adami@gmail.com>
collie.conf: provide a custom EXTRA_IMAGECMD_sum.jffs2

Match the changes to image_types.bbclass in oe-core.

REMARKS:

Q: the sum.jffs2 image is really smaller than the .jffs2
A: If you run sumtool with --pad parameter then it pads the OUTPUT file with
   0xFF to the end of the last used eraseblock.
   If you have empty eraseblocks at the end of your INPUT image then the sumtool
   skips those.

Signed-off-by: Andrea Adami <andrea.adami@gmail.com>