all: Update copyright header in all files

This patch updates copyright header in all files as follows:
1. Makes "SPDX-License-Identifier: BSD-2-Clause" as first line
2. Change copyright year to 2019 for Western Digital

Signed-off-by: Anup Patel <anup.patel@wdc.com>

Makefile

@@ -1,11 +1,11 @@
 #
-# Copyright (c) 2018 Western Digital Corporation or its affiliates.
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# Copyright (c) 2019 Western Digital Corporation or its affiliates.
 #
 # Authors:
 #   Anup Patel <anup.patel@wdc.com>
 #
-# SPDX-License-Identifier: BSD-2-Clause
-#
 
 # Current Version
 MAJOR = 0