[U-Boot] nios2 custodian

[Thomas Chou]

Dear Wolfgang,

Since Scott is very busy, I'd be willing to take over the maintenance of 
nios2 in u-boot.

I've been doing nios development for ten years. We work closely with 
Altera. I maintain nios2-linux, nios2-dev mailing list, the nios2 git 
repos and nios wiki, which is sponsored by Altera. Though I am new to 
this list, we maintained nios2 updates in our own git repo for years.

I will do my best to support the community. Thank you.

Best regards,
Thomas