[SMATCH] Can also be NULL false positive

["Ethan Tidmore" <ethantidmore06@gmail.com>]

Hi Dan,

Smatch gives these two warnings: 

drivers/gpu/drm/i915/display/intel_crtc.c:333 __intel_crtc_init() warn: 'primary' can also be NULL
drivers/gpu/drm/i915/display/intel_crtc.c:348 __intel_crtc_init() warn: 'plane' can also be NULL

	if (DISPLAY_VER(display) >= 9)
		primary = skl_universal_plane_create(display, pipe, PLANE_1);
	else
		primary = intel_primary_plane_create(display, pipe);
	if (IS_ERR(primary)) {
		ret = PTR_ERR(primary);
		goto fail;
	}
	crtc->plane_ids_mask |= BIT(primary->id);

and

		if (DISPLAY_VER(display) >= 9)
			plane = skl_universal_plane_create(display, pipe, PLANE_2 + sprite);
		else
			plane = intel_sprite_plane_create(display, pipe, sprite);
		if (IS_ERR(plane)) {
			ret = PTR_ERR(plane);
			goto fail;
		}
		crtc->plane_ids_mask |= BIT(plane->id);

But, this is a false positive because skl_universal_plane_create() and
intel_sprite_plane_create() never return NULL and always error pointers.

Thanks,

ET