drm/i915/cnp: Introduce Cannonpoint PCH.

Most of south engine display that is in PCH is still the
same as SPT and KBP, except for this key differences:

- Backlight: Backlight programming changed in CNP PCH.
- Panel Power: Sligh programming changed in CNP PCH.
- GMBUS and GPIO: The pin mapping has changed in CNP PCH.

All of these changes follow more the BXT style.

v2: Update definition to use dev_priv isntead of dev (Tvrtko).

Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1496434004-29812-1-git-send-email-rodrigo.vivi@intel.com

drivers/gpu/drm/i915/i915_drv.c

@@ -216,6 +216,9 @@ static void intel_detect_pch(struct drm_i915_private *dev_priv)
 				DRM_DEBUG_KMS("Found KabyPoint PCH\n");
 				WARN_ON(!IS_SKYLAKE(dev_priv) &&
 					!IS_KABYLAKE(dev_priv));
+			} else if (id == INTEL_PCH_CNP_DEVICE_ID_TYPE) {
+				dev_priv->pch_type = PCH_CNP;
+				DRM_DEBUG_KMS("Found CannonPoint PCH\n");
 			} else if ((id == INTEL_PCH_P2X_DEVICE_ID_TYPE) ||
 				   (id == INTEL_PCH_P3X_DEVICE_ID_TYPE) ||
 				   ((id == INTEL_PCH_QEMU_DEVICE_ID_TYPE) &&