drm/vc4: Fix compilation error reported by kbuild test bot

A pointer to crtc was missing, resulting in the following build error:
drivers/gpu/drm/vc4/vc4_crtc.c:1045:44: sparse: sparse: incorrect type in argument 1 (different base types)
drivers/gpu/drm/vc4/vc4_crtc.c:1045:44: sparse:    expected struct drm_crtc *crtc
drivers/gpu/drm/vc4/vc4_crtc.c:1045:44: sparse:    got struct drm_crtc_state *state
drivers/gpu/drm/vc4/vc4_crtc.c:1045:39: sparse: sparse: not enough arguments for function vc4_crtc_destroy_state

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reported-by: kbuild test robot <lkp@intel.com>
Cc: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/2b6ed5e6-81b0-4276-8860-870b54ca3262@linux.intel.com
Fixes: d0810679

 ("drm/vc4: Fix memory leak during gpu reset.")
Cc: <stable@vger.kernel.org> # v4.6+
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>