drm/radeon/kms: add thermal chip quirk for asus 9600xt

The board has an lm63 compatible thermal chip, but no
thermal chip entry in the vbios tables.

Fixes:
https://bugs.freedesktop.org/show_bug.cgi?id=39513



Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>