drm/bridge: Refactor out the panel wrapper from the lvds-encoder bridge.

Many DRM drivers have common code to make a stub connector
implementation that wraps a drm_panel.  By wrapping the panel in a DRM
bridge, all of the connector code (including calls during encoder
enable/disable) goes away.

v2: Fix build with CONFIG_DRM=m, drop "dev" argument that should just
    be the panel's dev, move kerneldoc up a level and document
    _remove().
v3: Fix another breakage with CONFIG_DRM=m, fix breakage with
    CONFIG_OF=n, move protos under CONFIG_DRM_PANEL_BRIDGE, wrap a
    line.

Signed-off-by: Eric Anholt <eric@anholt.net>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch> (v1)
Reviewed-by: Boris Brezillon <boris.brezillon@free-electrons.com> (v2)
Acked-by: Archit Taneja <architt@codeaurora.org> (v2)
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20170602202514.11900-1-eric@anholt.net
diff --git a/Documentation/gpu/drm-kms-helpers.rst b/Documentation/gpu/drm-kms-helpers.rst
index c075aad..7c5e254 100644
--- a/Documentation/gpu/drm-kms-helpers.rst
+++ b/Documentation/gpu/drm-kms-helpers.rst
@@ -143,6 +143,12 @@
 .. kernel-doc:: drivers/gpu/drm/drm_bridge.c
    :export:
 
+Panel-Bridge Helper Reference
+-----------------------------
+
+.. kernel-doc:: drivers/gpu/drm/bridge/panel.c
+   :export:
+
 .. _drm_panel_helper:
 
 Panel Helper Reference