Add support to logo images found in new mediatek devices.

[Teknosrp]

Hello

I am Teknosrp from xdadevelopers. A few months ago I wrote on your unpack/repack scripts thread about updating the scripts to support new logo images which use different color depth, and you asked me for submitting a pull request with the changes.

I have been busy and finally I had some free time, so I modified the scripts to support these new logo images while maintaining retrocompatibility. They seem to work properly, so now I'm trying to make the pull request. It's the first time that I'm using Git, so I hope I have done it correctly and I can start contributing to other projects.

Many thanks for your time and I wait for your answer.