powerpc: Update 83xx/85xx MAINTAINERS entry

Scott said he was still maintaining this "sort of", so change the
status to Odd Fixes.

Kumar has long ago moved on to greener pastures.

Remove the dead penguinppc.org link.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Scott Wood <oss@buserror.net>
Link: https://lore.kernel.org/r/20200224233146.23734-8-mpe@ellerman.id.au