drm/i915: extract intel_lvds.h from intel_drv.h

It used to be handy that we only had a couple of headers, but over time
intel_drv.h has become unwieldy. Extract declarations to a separate
header file corresponding to the implementation module, clarifying the
modularity of the driver.

Ensure the new header is self-contained, and do so with minimal further
includes, using forward declarations as needed. Include the new header
only where needed, and sort the modified include directives while at it
and as needed.

No functional changes.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/5d54d02cf7b7bfe3f78ed60d28534c5726371af3.1554461791.git.jani.nikula@intel.com

drivers/gpu/drm/i915/intel_drv.h

@@ -1881,13 +1881,6 @@ void intel_hpd_poll_init(struct drm_i915_private *dev_priv);
 bool intel_encoder_hotplug(struct intel_encoder *encoder,
 			   struct intel_connector *connector);
 
-/* intel_lvds.c */
-bool intel_lvds_port_enabled(struct drm_i915_private *dev_priv,
-			     i915_reg_t lvds_reg, enum pipe *pipe);
-void intel_lvds_init(struct drm_i915_private *dev_priv);
-struct intel_encoder *intel_get_lvds_encoder(struct drm_i915_private *dev_priv);
-bool intel_is_dual_link_lvds(struct drm_i915_private *dev_priv);
-
 /* intel_overlay.c */
 void intel_overlay_setup(struct drm_i915_private *dev_priv);
 void intel_overlay_cleanup(struct drm_i915_private *dev_priv);