drm/msm: Initial add eDP support in msm drm driver (v5)

This change adds a new eDP connector in msm drm driver. With this
change, eDP panel can work with msm platform under drm framework.

v1: Initial change

v2: Address Rob's comments
    Use generated header file for register definitions
    Change to devm_* APIs

v3: Address Thierry's comments and rebase on top of atomic changes
    Remove edp_bridge_mode_fixup
    Remove backlight control code and rely on pwm-backlight
    Remove continuous splash screen support for now
    Change to gpiod_* APIs

v4: Fix kbuild test issue

Signed-off-by: Hai Li <hali@codeaurora.org>
[robclark: v5: rebase on drm_bridge changes in drm-next]
Signed-off-by: Rob Clark <robdclark@gmail.com>
diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
index 22e5391..f0cb344 100644
--- a/drivers/gpu/drm/msm/msm_drv.h
+++ b/drivers/gpu/drm/msm/msm_drv.h
@@ -76,6 +76,12 @@
 	 */
 	struct hdmi *hdmi;
 
+	/* eDP is for mdp5 only, but kms has not been created
+	 * when edp_bind() and edp_init() are called. Here is the only
+	 * place to keep the edp instance.
+	 */
+	struct msm_edp *edp;
+
 	/* when we have more than one 'msm_gpu' these need to be an array: */
 	struct msm_gpu *gpu;
 	struct msm_file_private *lastctx;