drm/bridge: anx7625: Use common macros for HDCP capabilities

The DRM DP code has macros for the DP HDCP capabilities. Use them in the
anx7625 driver instead of raw numbers.

Fixes: cd1637c7 ("drm/bridge: anx7625: add HDCP support")
Suggested-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Reviewed-by: Robert Foss <rfoss@kernel.org>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230710091203.1874317-1-wenst@chromium.org

drivers/gpu/drm/bridge/analogix/anx7625.c

@@ -872,11 +872,11 @@ static int anx7625_hdcp_enable(struct anx7625_data *ctx)
 	}
 
 	/* Read downstream capability */
-	ret = anx7625_aux_trans(ctx, DP_AUX_NATIVE_READ, 0x68028, 1, &bcap);
+	ret = anx7625_aux_trans(ctx, DP_AUX_NATIVE_READ, DP_AUX_HDCP_BCAPS, 1, &bcap);
 	if (ret < 0)
 		return ret;
 
-	if (!(bcap & 0x01)) {
+	if (!(bcap & DP_BCAPS_HDCP_CAPABLE)) {
 		pr_warn("downstream not support HDCP 1.4, cap(%x).\n", bcap);
 		return 0;
 	}