drm/i915: Refactor EDID fixed mode search

Both LVDS and eDP have the same code to look up the preferred mode
from the connector probed_modes list. Move the code to a common
location.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190321132446.22394-1-ville.syrjala@linux.intel.com
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/intel_drv.h

@@ -2157,6 +2157,8 @@ extern struct drm_display_mode *intel_find_panel_downclock(
 				struct drm_i915_private *dev_priv,
 				struct drm_display_mode *fixed_mode,
 				struct drm_connector *connector);
+struct drm_display_mode *
+intel_panel_edid_fixed_mode(struct intel_connector *connector);
 
 #if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE)
 int intel_backlight_device_register(struct intel_connector *connector);