drm/atomic: Update comment to match the code

The kerneldoc for drm_atomic_crtc_needs_modeset() is outdated and no
longer reflects the actual code. Fix that up to remove confusion.
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NThierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170731091343.21363-1-thierry.reding@gmail.com

include/drm/drm_atomic.h

@@ -883,7 +883,7 @@ void drm_state_dump(struct drm_device *dev, struct drm_printer *p);
  *
  * To give drivers flexibility &struct drm_crtc_state has 3 booleans to track
  * whether the state CRTC changed enough to need a full modeset cycle:
- * planes_changed, mode_changed and active_changed. This helper simply
+ * mode_changed, active_changed and connectors_changed. This helper simply
  * combines these three to compute the overall need for a modeset for @state.
  *
  * The atomic helper code sets these booleans, but drivers can and should