drm/nouveau/bios: memset dcb struct to zero before parsing
drm/nouveau/bios: memset dcb struct to zero before parsing

Fixes type/mask calculation being based on uninitialised data for VGA
outputs.

Signed-off-by: Ben Skeggs <d9f27fb07c1e9f131223ad827fa5179f3846c30b@redhat.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs