lenovo: add config ONBOARD_VGA_IS_PRIMARY

Fix for the T4xx and T5xx series.
It does not apply to X2xx/X6x series as those have only
one GPU, which is always connected to the display.

The T6x series needs special care not handled with this patch.

Without ONBOARD_VGA_IS_PRIMARY the onboard GPU would be
deactivated in case a dedicated GPU is found and active,
leaving the system without a working display.

Change-Id: I94d1700e9afb75de83a4f2ed1ff53ba3b0559ae1
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/14031
Tested-by: build bot (Jenkins)
Reviewed-by: Alexander Couzens <lynxis@fe80.eu>
Reviewed-by: Nicolas Reinecke <nr@das-labor.org>

src/mainboard/lenovo/t400/Kconfig

@@ -51,4 +51,8 @@ config CBFS_SIZE
 	hex
 	default 0x200000
 
+config ONBOARD_VGA_IS_PRIMARY
+	bool
+	default y
+
 endif # BOARD_LENOVO_T400

src/mainboard/lenovo/t420s/Kconfig

@@ -70,4 +70,8 @@ config MAINBOARD_PCI_SUBSYSTEM_DEVICE_ID
 	hex
 	default 0x21d2
 
+config ONBOARD_VGA_IS_PRIMARY
+	bool
+	default y
+
 endif # BOARD_LENOVO_T420S

src/mainboard/lenovo/t430s/Kconfig

@@ -67,4 +67,8 @@ config MAINBOARD_PCI_SUBSYSTEM_DEVICE_ID
 	hex
 	default 0x21fb
 
+config ONBOARD_VGA_IS_PRIMARY
+	bool
+	default y
+
 endif # BOARD_LENOVO_T430S

src/mainboard/lenovo/t520/Kconfig

@@ -70,4 +70,8 @@ config MAINBOARD_PCI_SUBSYSTEM_DEVICE_ID
 	hex
 	default 0x21cf
 
+config ONBOARD_VGA_IS_PRIMARY
+	bool
+	default y
+
 endif # BOARD_LENOVO_T520

src/mainboard/lenovo/t530/Kconfig

@@ -68,4 +68,8 @@ config MAINBOARD_PCI_SUBSYSTEM_DEVICE_ID
 	hex
 	default 0x21fa
 
+config ONBOARD_VGA_IS_PRIMARY
+	bool
+	default y
+
 endif # BOARD_LENOVO_T530