spi: atmel-quadspi: switch to SPDX license identifiers

Adopt the SPDX license identifiers to ease license compliance
management.
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Boris Brezillon <bbrezillon@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/atmel-quadspi.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * Driver for Atmel QSPI Controller
  *
@@ -7,18 +8,6 @@
  * Author: Cyrille Pitchen <cyrille.pitchen@atmel.com>
  * Author: Piotr Bugalski <bugalski.piotr@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/>.
- *
  * This driver is based on drivers/mtd/spi-nor/fsl-quadspi.c from Freescale.
  */