drm/nouveau/kms/nv50-: Use drm_dp_dpcd_(readb|writeb)() in nv50_sor_disable()

Just use drm_dp_dpcd_(readb|writeb)() so we get automatic DPCD logging
Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Ben Skeggs <bskeggs@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200826182456.322681-8-lyude@redhat.com

drivers/gpu/drm/nouveau/dispnv50/disp.c

@@ -1630,19 +1630,22 @@ nv50_sor_disable(struct drm_encoder *encoder,
 {
 	struct nouveau_encoder *nv_encoder = nouveau_encoder(encoder);
 	struct nouveau_crtc *nv_crtc = nouveau_crtc(nv_encoder->crtc);
+	struct nouveau_connector *nv_connector =
+		nv50_outp_get_old_connector(nv_encoder, state);
 
 	nv_encoder->crtc = NULL;
 
 	if (nv_crtc) {
-		struct nvkm_i2c_aux *aux = nv_encoder->aux;
+		struct drm_dp_aux *aux = &nv_connector->aux;
 		u8 pwr;
 
-		if (aux) {
-			int ret = nvkm_rdaux(aux, DP_SET_POWER, &pwr, 1);
+		if (nv_encoder->dcb->type == DCB_OUTPUT_DP) {
+			int ret = drm_dp_dpcd_readb(aux, DP_SET_POWER, &pwr);
+
 			if (ret == 0) {
 				pwr &= ~DP_SET_POWER_MASK;
 				pwr |=  DP_SET_POWER_D3;
-				nvkm_wraux(aux, DP_SET_POWER, &pwr, 1);
+				drm_dp_dpcd_writeb(aux, DP_SET_POWER, pwr);
 			}
 		}