drm/atomic-helper: Massage swap_state signature somewhat

- dev is redundant, we have state->atomic
- add stall parameter, which must be set when swapping needs to stall
  for preceeding commits to stop looking at ->state pointers. Currently
  all drivers need this to be, just prep work for a glorious future.

v2: Rebased on top of

commit e7cf0963f816fa44190caaf51aeffaa614c340c6
Author: Gerd Hoffmann <kraxel@redhat.com>
Date:   Tue May 31 08:50:47 2016 +0200

    virtio-gpu: add atomic_commit function

Cc: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1465509992-19284-1-git-send-email-daniel.vetter@ffwll.ch
Link: http://patchwork.freedesktop.org/patch/msgid/1465388359-8070-2-git-send-email-daniel.vetter@ffwll.ch
diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 4b2c1d2..aa2cad9 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1167,7 +1167,7 @@
 	 * the software side now.
 	 */
 
-	drm_atomic_helper_swap_state(dev, state);
+	drm_atomic_helper_swap_state(state, true);
 
 	/*
 	 * Everything below can be run asynchronously without the need to grab
@@ -1538,8 +1538,8 @@
 
 /**
  * drm_atomic_helper_swap_state - store atomic state into current sw state
- * @dev: DRM device
  * @state: atomic state
+ * @stall: stall for proceeding commits
  *
  * This function stores the atomic state into the current state pointers in all
  * driver objects. It should be called after all failing steps have been done
@@ -1561,8 +1561,8 @@
  * 5. Call drm_atomic_helper_cleanup_planes() with @state, which since step 3
  * contains the old state. Also do any other cleanup required with that state.
  */
-void drm_atomic_helper_swap_state(struct drm_device *dev,
-				  struct drm_atomic_state *state)
+void drm_atomic_helper_swap_state(struct drm_atomic_state *state,
+				  bool stall)
 {
 	int i;
 	struct drm_connector *connector;