Revert "drivers/ddr/fsl: Dual-license DDR driver"

Upon further review, not all code authors are in favour of this change.
This reverts commit ee3556bcafbb05e59aabdc31368984e76acaabc4.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/include/fsl_ddr_dimm_params.h b/include/fsl_ddr_dimm_params.h
index af673fd..1632a8f 100644
--- a/include/fsl_ddr_dimm_params.h
+++ b/include/fsl_ddr_dimm_params.h
@@ -2,7 +2,7 @@
  * Copyright 2008-2016 Freescale Semiconductor, Inc.
  * Copyright 2017-2018 NXP Semiconductor
  *
- * SPDX-License-Identifier:	GPL-2.0	BSD-3-Clause
+ * SPDX-License-Identifier:	GPL-2.0
  */
 
 #ifndef DDR2_DIMM_PARAMS_H