drm/panel: Fix sphinx warning

Resolves the following warnings.
../drivers/gpu/drm/drm_panel.c:158: WARNING: Unexpected indentation.
../drivers/gpu/drm/drm_panel.c:159: WARNING: Block quote ends without a blank line; unexpected unindent.

Fixes: c59eb3cfde1f ("drm/panel: Let of_drm_find_panel() return -ENODEV when the panel is disabled")
Cc: Boris Brezillon <boris.brezillon@bootlin.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Jyri Sarha <jsarha@ti.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20180815203833.210143-1-sean@poorly.run

drivers/gpu/drm/drm_panel.c

@@ -152,7 +152,9 @@ EXPORT_SYMBOL(drm_panel_detach);
  *
  * Return: A pointer to the panel registered for the specified device tree
  * node or an ERR_PTR() if no panel matching the device tree node can be found.
+ *
  * Possible error codes returned by this function:
+ *
  * - EPROBE_DEFER: the panel device has not been probed yet, and the caller
  *   should retry later
  * - ENODEV: the device is not available (status != "okay" or "ok")