scripts: rename om2p-fwupgradecfg-gen.sh to more generic om-fwupgradecfg-gen.sh

It will be used for non OM2P boards as well.

Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

SVN-Revision: 34200