rk3288: Auto-detect display.

We currently select either HDMI or EDP (default). This patch
allows us to use HDMI as a fallback for devices that may have
a display connected on either interface. It also renames the
enums to sound a little more sensible in other contexts (more
on that in the follow-up patches).

VOP_MODE_AUTO is added to the mode enum which will make it explicit
that a board can support either. In AUTO_MODE we will try EDP first
and then fallback to HDMI. Other modes can be set to force a certain
behavior such as HDMI-only on Mickey where it doesn't make sense to
try EDP.

A follow-up patch will add logic for when we explicitly don't want
to probe for any display (headless devices).

BUG=none
BRANCH=none
TEST=On veyron_danger, connected EDP and HDMI displays and saw dev
mode screen appear on EDP display. Unplugged EDP and then dev mode
screen showed up on HDMI.

Change-Id: I22b38031c4ab3d79fbb182f7a906da1197f35543
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 3f57ed3758c4e516d9fd226ad9499b102b81b423
Original-Change-Id: I352dcde16f7f3ebbf5796852b685685e541eb794
Original-Signed-off-by: David Hendricks <dhendrix@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/281076
Original-Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: http://review.coreboot.org/10775
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
diff --git a/src/soc/rockchip/rk3288/chip.h b/src/soc/rockchip/rk3288/chip.h
index 3a6b14d..2c4390a 100644
--- a/src/soc/rockchip/rk3288/chip.h
+++ b/src/soc/rockchip/rk3288/chip.h
@@ -21,6 +21,7 @@
 #define __SOC_ROCKCHIP_RK3288_CHIP_H__
 
 #include <soc/gpio.h>
+#include <soc/vop.h>	/* for vop_modes enum used in devicetree.cb */
 
 struct soc_rockchip_rk3288_config {
 	u32 vop_id;