drm: Fixup failure paths in drm_atomic_helper_set_config

I've screwed this up when removing the legacy backoff hack.

Fixes: 38b6441e4e75 ("drm/atomic-helper: Remove the backoff hack from set_config")
Cc: Harry Wentland <[e-mail]>
Cc: Daniel Vetter <[e-mail]>
Cc: Daniel Vetter <[e-mail]>
Cc: Jani Nikula <[e-mail]>
Cc: Sean Paul <[e-mail]>
Cc: David Airlie <[e-mail]>
Cc: [e-mail]
Reviewed-by: Harry Wentland <[e-mail]>
Signed-off-by: Daniel Vetter <[e-mail]>
Link: http://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/drm_atomic_helper.c

···
 	state->acquire_ctx = ctx;
 	ret = __drm_atomic_helper_set_config(set, state);
 	if (ret != 0)
-		return ret;
+		goto fail;
 
 	ret = drm_atomic_commit(state);
 
+fail:
 	drm_atomic_state_put(state);
 	return ret;
 }