Without this header, the newly added code fails to build:

drivers/gpu/drm/rockchip/rk3066_hdmi.c: In function 'rk3066_hdmi_encoder_enable':
drivers/gpu/drm/rockchip/rk3066_hdmi.c:397:22: error: implicit declaration of function 'drm_atomic_get_new_connector_state'; did you mean 'drm_atomic_helper_connector_reset'? [-Werror=implicit-function-declaration]
  397 |         conn_state = drm_atomic_get_new_connector_state(state, &hdmi->connector);
      |                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      |                      drm_atomic_helper_connector_reset
drivers/gpu/drm/rockchip/rk3066_hdmi.c:397:20: error: assignment to 'struct drm_connector_state *' from 'int' makes pointer from integer without a cast [-Werror=int-conversion]
  397 |         conn_state = drm_atomic_get_new_connector_state(state, &hdmi->connector);
      |                    ^
drivers/gpu/drm/rockchip/rk3066_hdmi.c:401:22: error: implicit declaration of function 'drm_atomic_get_new_crtc_state'; did you mean 'drm_atomic_helper_swap_state'? [-Werror=implicit-function-declaration]
  401 |         crtc_state = drm_atomic_get_new_crtc_state(state, conn_state->crtc);
      |                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      |                      drm_atomic_helper_swap_state
drivers/gpu/drm/rockchip/rk3066_hdmi.c:401:20: error: assignment to 'struct drm_crtc_state *' from 'int' makes pointer from integer without a cast [-Werror=int-conversion]
  401 |         crtc_state = drm_atomic_get_new_crtc_state(state, conn_state->crtc);
      |                    ^

Fixes: ae3436a5 ("drm/rockchip: rk3066_hdmi: Switch encoder hooks to atomic")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20231122221838.3164349-1-arnd@kernel.org