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/hw-gfx-gma-display_probing.adb b/common/hw-gfx-gma-display_probing.adb
index 72df4ed..673f0ad 100644
--- a/common/hw-gfx-gma-display_probing.adb
+++ b/common/hw-gfx-gma-display_probing.adb
@@ -19,6 +19,7 @@
 with HW.GFX.GMA.I2C;
 with HW.GFX.GMA.DP_Aux_Ch;
 with HW.GFX.GMA.Panel;
+with HW.GFX.GMA.Connectors;
 with HW.GFX.GMA.Port_Detect;
 with HW.GFX.GMA.Power_And_Clocks;