plat: imx: fix the license issue for imx8m

Clean up & Fix the license issue
Signed-off-by: Jacky Bai <ping.bai@nxp.com>

plat/imx/common/imx8m/ddr4_retention.c

 /*
- * copyright 2018 nxp
+ * Copyright 2017-2019 NXP
  *
- * spdx-license-identifier: bsd-3-clause
+ * SPDX-License-Identifier: BSD-3-Clause
  */
 
 #include <arch.h>

plat/imx/imx8mm/include/ddrc.h

+/*
+ * Copyright 2017-2019 NXP
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
 #ifndef __IMX_DDRC_H
 #define __IMX_DDRC_H
 

plat/imx/imx8mm/include/platform_def.h

+/*
+ * Copyright 2017-2019 NXP
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
 #define PLATFORM_LINKER_FORMAT		"elf64-littleaarch64"
 #define PLATFORM_LINKER_ARCH		aarch64
 

plat/imx/imx8mq/include/ddrc.h

+/*
+ * Copyright 2017-2019 NXP
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
 #ifndef __IMX_DDRC_H
 #define __IMX_DDRC_H
 

plat/imx/imx8mq/include/platform_def.h

+/*
+ * Copyright 2017-2019 NXP
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
 #define PLATFORM_LINKER_FORMAT		"elf64-littleaarch64"
 #define PLATFORM_LINKER_ARCH		aarch64