drm/radeon: fix firmware info version checks

commit 3edc38a0facef45ee22af8afdce3737f421f36ab upstream.

Some of the checks didn't handle frev 2 tables properly.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Willy Tarreau <w@1wt.eu>