update dm7020hd secondstage loader
- fixed ineffective front usb port
- fixed wrong frontpanel key handling
- prepare for new kernel versions
dreambox-secondstage: allow kernel commandline override for dm7020hd again
add mtd-utils-flasherase and mtd-utils-nandwrite to rdepends
update dm7020hd to 87 (added DM7020HDv2 support), cleanup recipe, build secondstage.nfi on the fly, add depends to writenfi and buildimage tool
update dm7020hdv2 secondstage to version 88 (changed display logos)
update dm500hdv2/dm800sev2/dm7020hd secondstage loader to support different flash types