drm/etnaviv: remove unused iommu_v2 header

This has been there from the original merge, but has never been used.
Get rid of it.
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>

drivers/gpu/drm/etnaviv/etnaviv_iommu_v2.h

-/*
- * Copyright (C) 2014 Christian Gmeiner <christian.gmeiner@gmail.com>
-  *
- * This program is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License version 2 as published by
- * the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
- * more details.
- *
- * You should have received a copy of the GNU General Public License along with
- * this program.  If not, see <http://www.gnu.org/licenses/>.
- */
-
-#ifndef __ETNAVIV_IOMMU_V2_H__
-#define __ETNAVIV_IOMMU_V2_H__
-
-#include <linux/iommu.h>
-struct etnaviv_gpu;
-
-struct iommu_domain *etnaviv_iommu_v2_domain_alloc(struct etnaviv_gpu *gpu);
-
-#endif /* __ETNAVIV_IOMMU_V2_H__ */