drm/i915: Remove check for !crtc_state in intel_plane_atomic_calc_changes()

smatch spotted that:

	drivers/gpu/drm/i915/intel_display.c:11986
	intel_plane_atomic_calc_changes() warn: variable dereferenced before
	check 'crtc_state' (see line 11972)

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1467470166-31717-9-git-send-email-chris@chris-wilson.co.uk
Reviewed-by: Matthew Auld <matthew.auld@intel.com>

drivers/gpu/drm/i915/intel_display.c

@@ -11983,8 +11983,7 @@ int intel_plane_atomic_calc_changes(struct drm_crtc_state *crtc_state,
 	struct drm_framebuffer *fb = plane_state->fb;
 	int ret;
 
-	if (crtc_state && INTEL_INFO(dev)->gen >= 9 &&
-	    plane->type != DRM_PLANE_TYPE_CURSOR) {
+	if (INTEL_GEN(dev) >= 9 && plane->type != DRM_PLANE_TYPE_CURSOR) {
 		ret = skl_update_scaler_plane(
 			to_intel_crtc_state(crtc_state),
 			to_intel_plane_state(plane_state));