drm/vc4: Switch to drm_atomic_get_new_crtc_state()

The vc4 atomic_check implementation uses the deprecated
drm_atomic_get_existing_crtc_state() helper.

This hook is called as part of the global atomic_check, thus before the
states are swapped. The existing state thus points to the new state, and
we can use drm_atomic_get_new_crtc_state() instead.

Reviewed-by: Ville Syrjälä <[e-mail]>
Acked-by: Dave Stevenson <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Maxime Ripard <[e-mail]>

drivers/gpu/drm/vc4/vc4_plane.c

···
 	u32 v_subsample = fb->format->vsub;
 	int ret;
 
-	crtc_state = drm_atomic_get_existing_crtc_state(state->state,
-							state->crtc);
+	crtc_state = drm_atomic_get_new_crtc_state(state->state, state->crtc);
 	if (!crtc_state) {
 		DRM_DEBUG_KMS("Invalid crtc state\n");
 		return -EINVAL;
···
 	unsigned int vscale_factor;
 
 	vc4_state = to_vc4_plane_state(state);
-	crtc_state = drm_atomic_get_existing_crtc_state(state->state,
-							state->crtc);
+	crtc_state = drm_atomic_get_new_crtc_state(state->state, state->crtc);
 	vrefresh = drm_mode_vrefresh(&crtc_state->adjusted_mode);
 
 	/* The HVS is able to process 2 pixels/cycle when scaling the source,