[Qemu-arm] TCG AArch64 target maintained status change

[Claudio Fontana]

Hello all,

the last bug report from Alex pointed me to the fact that I am unable to focus 
on TCG AArch64 maintenance, due to changed working conditions since some time 
now.

I think that in practice Richard has been taking care of this module anyway, so 
I think it is time to make it official.
Should I send a patch to change Maintained to Orphaned for the MAINTAINERS file?
Or maybe Peter, Richard you can directly appoint the replacement name in there?

Thanks,

Claudio