MAINTAINERS: update entry for MMP platform

MAINTAINERS: update entry for MMP platform

Move Eric Miao and Haojian Zhuang over to CREDITS, since they're AWOL
for some time already. The git trees have gone away too.

I'm adding myself as a reviewer. I'd like to be Cc'd on patches and will
be able to test them, but I don't possess a data sheet thus there might
be things I'll be unable to review. Hence the Odd-Fixes status.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Signed-off-by: Olof Johansson <olof@lixom.net>