drm/amd/display: Add missing chips for HDCP

[WHAT]
Add missing HDCP ID in the message id enum.

Acked-by: Alex Hung <[e-mail]>
Signed-off-by: Rodrigo Siqueira <[e-mail]>
Tested-by: Daniel Wheeler <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/display/include/hdcp_msg_types.h

···
 	HDCP_MESSAGE_ID_READ_RXSTATUS,
 	HDCP_MESSAGE_ID_WRITE_CONTENT_STREAM_TYPE,
 
+	/* PS175 chip */
+
+	HDCP_MESSAGE_ID_WRITE_PS175_CMD,
+	HDCP_MESSAGE_ID_READ_PS175_RSP,
+
 	HDCP_MESSAGE_ID_MAX
 };