clk: mvebu: armada-37xx-periph: switch to SPDX license identifier

Adopt the SPDX license identifier headers to ease license compliance
management.
Signed-off-by: NGregory CLEMENT <gregory.clement@bootlin.com>
Signed-off-by: NStephen Boyd <sboyd@kernel.org>

drivers/clk/mvebu/armada-37xx-periph.c

+// SPDX-License-Identifier: GPL-2.0+
 /*
  * Marvell Armada 37xx SoC Peripheral clocks
  *
@@ -5,10 +6,6 @@
  *
  * Gregory CLEMENT <gregory.clement@free-electrons.com>
  *
- * This file is licensed under the terms of the GNU General Public
- * License version 2 or later. This program is licensed "as is"
- * without any warranty of any kind, whether express or implied.
- *
  * Most of the peripheral clocks can be modelled like this:
  *             _____    _______    _______
  * TBG-A-P  --|     |  |       |  |       |   ______