drm/vc4: Allocate the right amount of space for boot-time CRTC state.

Without this, the first modeset would dereference past the allocation
when trying to free the mm node.
Signed-off-by: Eric Anholt <eric@anholt.net>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170328201343.4884-1-eric@anholt.net
Fixes: d8dbf44f ("drm/vc4: Make the CRTCs cooperate on allocating display lists.")
Cc: <stable@vger.kernel.org> # v4.6+
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/vc4/vc4_crtc.c

@@ -846,6 +846,17 @@ static void vc4_crtc_destroy_state(struct drm_crtc *crtc,
 	drm_atomic_helper_crtc_destroy_state(crtc, state);
 }
 
+static void
+vc4_crtc_reset(struct drm_crtc *crtc)
+{
+	if (crtc->state)
+		__drm_atomic_helper_crtc_destroy_state(crtc->state);
+
+	crtc->state = kzalloc(sizeof(struct vc4_crtc_state), GFP_KERNEL);
+	if (crtc->state)
+		crtc->state->crtc = crtc;
+}
+
 static const struct drm_crtc_funcs vc4_crtc_funcs = {
 	.set_config = drm_atomic_helper_set_config,
 	.destroy = vc4_crtc_destroy,
@@ -853,7 +864,7 @@ static const struct drm_crtc_funcs vc4_crtc_funcs = {
 	.set_property = NULL,
 	.cursor_set = NULL, /* handled by drm_mode_cursor_universal */
 	.cursor_move = NULL, /* handled by drm_mode_cursor_universal */
-	.reset = drm_atomic_helper_crtc_reset,
+	.reset = vc4_crtc_reset,
 	.atomic_duplicate_state = vc4_crtc_duplicate_state,
 	.atomic_destroy_state = vc4_crtc_destroy_state,
 	.gamma_set = vc4_crtc_gamma_set,