Remove support for IDT. Only the RouterBoard RB533 used this chip, and
it's at least 5 years out of production. I couldn't find a used one on
ebay and other secondary markets just now, nor when I tried 4 years
ago. It dates from the initial project/mips2 merge 8 years ago, and
hasn't been updated since.
Discussed on: mips@ (with some dissent)