drm: Move drm_plane_helper_check_state() into drm_atomic_helper.c

drm_plane_helper_check_update() isn't a transitional helper, so let's
rename it to drm_atomic_helper_check_plane_state() and move it into
drm_atomic_helper.c.

v2: Fix the WARNs about plane_state->crtc matching crtc_state->crtc

Cc: Daniel Vetter <daniel@ffwll.ch>
Suggested-by: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171101201619.6175-1-ville.syrjala@linux.intel.com
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 5e75d76..9740616 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -9418,12 +9418,12 @@ static int intel_check_cursor(struct intel_crtc_state *crtc_state,
 	u32 offset;
 	int ret;
 
-	ret = drm_plane_helper_check_state(&plane_state->base,
-					   &crtc_state->base,
-					   &plane_state->clip,
-					   DRM_PLANE_HELPER_NO_SCALING,
-					   DRM_PLANE_HELPER_NO_SCALING,
-					   true, true);
+	ret = drm_atomic_helper_check_plane_state(&plane_state->base,
+						  &crtc_state->base,
+						  &plane_state->clip,
+						  DRM_PLANE_HELPER_NO_SCALING,
+						  DRM_PLANE_HELPER_NO_SCALING,
+						  true, true);
 	if (ret)
 		return ret;
 
@@ -12842,11 +12842,11 @@ intel_check_primary_plane(struct intel_plane *plane,
 		can_position = true;
 	}
 
-	ret = drm_plane_helper_check_state(&state->base,
-					   &crtc_state->base,
-					   &state->clip,
-					   min_scale, max_scale,
-					   can_position, true);
+	ret = drm_atomic_helper_check_plane_state(&state->base,
+						  &crtc_state->base,
+						  &state->clip,
+						  min_scale, max_scale,
+						  can_position, true);
 	if (ret)
 		return ret;