gma connectors: Add a Prepare() step

Prepare() will be used to adapt a `Port_Config' to platform quirks.
For instance the FDI usage on Ironlake, USB-C usage on Tiger Lake.

Change-Id: I2fb3ed026077f0371112682b90bea751a28bf994
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.sourcearcade.org/c/libgfxinit/+/462
Tested-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
diff --git a/common/ironlake/hw-gfx-gma-connectors.adb b/common/ironlake/hw-gfx-gma-connectors.adb
index 1c3a243..db8e6d0 100644
--- a/common/ironlake/hw-gfx-gma-connectors.adb
+++ b/common/ironlake/hw-gfx-gma-connectors.adb
@@ -32,6 +32,19 @@
    procedure Post_Reset_Off is null;
    procedure Initialize is null;
 
+   ----------------------------------------------------------------------------
+
+   procedure Prepare
+     (Port     : in     Active_Port_Type;
+      Port_Cfg : in out Port_Config;
+      Success  :    out Boolean)
+   is
+   begin
+      Success := True;
+   end Prepare;
+
+   ----------------------------------------------------------------------------
+
    function Is_Internal (Port_Cfg : Port_Config) return Boolean
    is
    begin