drm/framebuffer: Switch to drm_atomic_get_new_crtc_state()

The atomic_remove_fb() function uses the deprecated
drm_atomic_get_existing_crtc_state() helper.

Despite its name, this function builds and commit a new
drm_atomic_state, and the call to drm_atomic_get_existing_crtc_state()
is part of the state building, thus happening before the states are
swapped.

As such, the existing state points to the new state, and we can use
drm_atomic_get_new_crtc_state() instead.

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

drivers/gpu/drm/drm_framebuffer.c

···
 				    plane_state->crtc->base.id,
 				    plane_state->crtc->name, fb->base.id);
 
-			crtc_state = drm_atomic_get_existing_crtc_state(state, plane_state->crtc);
+			crtc_state = drm_atomic_get_new_crtc_state(state, plane_state->crtc);
 
 			ret = drm_atomic_add_affected_connectors(state, plane_state->crtc);
 			if (ret)