mb/apple/macbookair4_2: Correct internal video port selection

The MacBook Air 4,2 uses eDP, according to the schematics.

Change-Id: Ifc98eab343fd89b8512e92e01fddf34ef8447d5f
Signed-off-by: Evgeny Zinoviev <me@ch1p.io>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32606
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/apple/macbookair4_2/Kconfig

@@ -12,7 +12,7 @@ config BOARD_SPECIFIC_OPTIONS
 	select SERIRQ_CONTINUOUS_MODE
 	select SOUTHBRIDGE_INTEL_BD82X6X
 	select SYSTEM_TYPE_LAPTOP
-	select GFX_GMA_INTERNAL_IS_LVDS
+	select GFX_GMA_INTERNAL_IS_EDP
 	select MAINBOARD_HAS_LIBGFXINIT
 
 config MAINBOARD_DIR