gma panel: Introduce `Panel_Control` type

For now, `Panel_Control` only distinguishes `Panel_1` from `No_Panel`,
i.e. if a port has a panel attached or not. To ease future addition of
support for more than one panel, we already add loops and arrays around
it, though.

With the information, if a port has a panel attached, in `Port_Config`,
we can pass that on into Panel.* procedures and let those decide what
to do (e.g. do nothing if no panel is attached).

Change-Id: I83864bc86b48f65d9ba43e083b805ca09497cbb0
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/c/libgfxinit/+/38243
Tested-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
diff --git a/common/hw-gfx-gma-config_helpers.ads b/common/hw-gfx-gma-config_helpers.ads
index 9d689c7..b9f1d70 100644
--- a/common/hw-gfx-gma-config_helpers.ads
+++ b/common/hw-gfx-gma-config_helpers.ads
@@ -13,6 +13,7 @@
 --
 
 with HW;
+with HW.GFX.GMA.Config;
 
 private package HW.GFX.GMA.Config_Helpers
 is
@@ -26,6 +27,8 @@
 
    function To_Display_Type (Port : Active_Port_Type) return Display_Type;
 
+   function To_Panel (Port : Active_Port_Type) return Panel_Control;
+
    procedure Fill_Port_Config
      (Port_Cfg :    out Port_Config;
       Pipe     : in     Pipe_Index;