drivers/lenovo: Add hybrid graphics driver

Add a universal hybrid graphics driver compatible with
all supported lenovo devices.
Hybrid graphics allows to connect the display panel to
either of one GPUs.
As there are only two GPUs one GPIO needs to be toggled.
In case the discrete GPU is activated the panel is routed to it.
On deactivation the panel is routed to the integrated
GPU.
On lenovo laptops the dGPU is always connected to PEG10 and it is
save to disable the PEG slot on dGPU deactivation.

Use common gpio.c for southbridge I82801IX.

Tested on Lenovo T520 using Nvidia NVS 5200m.

Removed Lenovo T430s from the list of supported devices,
as the T430s only supports "muxless Optimus".

Depends on change id:
Iccc6d254bafb927b6470704cec7c9dd7528e2c68
Ibb54c03fd83a529d1ceccfb2c33190e7d42224d8
I8bd981c4696c174152cf41caefa6c083650d283a
Iaf0c2f941f2625a5547f9cba79da1b173da6f295
I994114734fa931926c34ed04305cddfbeb429b62

Change-Id: I9b80b31a7749bdf893ed3b772a6505c9f29a56d1
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/12896
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>
Reviewed-by: Philipp Deppenwiese <zaolin.daisuki@googlemail.com>
diff --git a/src/mainboard/lenovo/t420s/Kconfig b/src/mainboard/lenovo/t420s/Kconfig
index 935e659..feacb51 100644
--- a/src/mainboard/lenovo/t420s/Kconfig
+++ b/src/mainboard/lenovo/t420s/Kconfig
@@ -18,6 +18,7 @@
 	select INTEL_INT15
 	select SANDYBRIDGE_IVYBRIDGE_LVDS
 	select MAINBOARD_HAS_LPC_TPM
+	select DRIVERS_LENOVO_HYBRID_GRAPHICS
 
 	# Workaround for EC/KBC IRQ1.
 	select SERIRQ_CONTINUOUS_MODE