buildman: Fetch 12.2.0 toolchains by default

Update the toolchain list to be first 12.2.0 and second 11.1.0 and
that's it.

Cc: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>