drm/nouveau/disp/mcp7x: disable dptmds workaround

The workaround appears to cause regressions on these boards, and from
inspection of RM traces, NVIDIA don't appear to do it on them either.

Signed-off-by: Ben Skeggs <[e-mail]>
Tested-by: Roy Spliet <[e-mail]>

drivers/gpu/drm/nouveau/nvkm/engine/disp/nv50.c

···
 	case 0x94:
 	case 0x96:
 	case 0x98:
-	case 0xaa:
-	case 0xac:
 		return true;
 	default:
 		break;