mb/asrock/b85m_pro4/gma-mainboard.ads: Use GPL-2.0-or-later

Other files in the tree use such license. I first added this file.

Change-Id: I338654ec022bd6f2fa4a4381a8f27d024605e79d
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/41525
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

src/mainboard/asrock/b85m_pro4/gma-mainboard.ads

@@ -1,4 +1,4 @@
--- SPDX-License-Identifier: GPL-2.0-only
+-- SPDX-License-Identifier: GPL-2.0-or-later
 
 with HW.GFX.GMA;
 with HW.GFX.GMA.Display_Probing;