gma: Refactor Hotplug_Detect() interface and usage

Checking for hotplug events should be done before any other work to
reduce load and (spurious) debug output. Therefor, use the simpler
`Port_Type` in the interface of `Hotplug_Detect()` so we don't have to
fill the whole `Port_Cfg` before checking for events.

Also, now that it's possible, factor the disabling of a single output
out of `Update_Outputs()`.

Change-Id: I2a0ba5530c8d511fa95f9cac12297ad428a40d77
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/18119
Tested-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
diff --git a/common/hw-gfx-gma-port_detect.ads b/common/hw-gfx-gma-port_detect.ads
index c9d339b..1cd8d6b 100644
--- a/common/hw-gfx-gma-port_detect.ads
+++ b/common/hw-gfx-gma-port_detect.ads
@@ -1,5 +1,5 @@
 --
--- Copyright (C) 2016 secunet Security Networks AG
+-- Copyright (C) 2016-2017 secunet Security Networks AG
 --
 -- This program is free software; you can redistribute it and/or modify
 -- it under the terms of the GNU General Public License as published by
@@ -16,6 +16,8 @@
 
    procedure Initialize;
 
-   procedure Hotplug_Detect (Port_Cfg : in Port_Config; Detected : out Boolean);
+   procedure Hotplug_Detect
+     (Port     : in Active_Port_Type;
+      Detected : out Boolean);
 
 end HW.GFX.GMA.Port_Detect;