Add SPDX license tag to the ENA driver files

Refering to guide: https://wiki.freebsd.org/SPDX the SPDX tag should not
replace the standard license text, however it should be added over the
standard license text to make the automation easier.

Because of that, the old license was kept, but the SPDX tag was added
on top of every ENA driver file.

Submited by:    Michal Krawczyk <mk@semihalf.com>
Obtained from:  Semihalf
Sponsored by:   Amazon, Inc
MFC after:      1 week
Differential revision:  https://reviews.freebsd.org/D27117

share/man/man4/ena.4

@@ -1,4 +1,6 @@
-.\" Copyright (c) 2015-2017 Amazon.com, Inc. or its affiliates.
+.\" SPDX-License-Identifier: BSD-2-Clause
+.\"
+.\" Copyright (c) 2015-2020 Amazon.com, Inc. or its affiliates.
 .\" All rights reserved.
 .\"
 .\" Redistribution and use in source and binary forms, with or without

sys/dev/ena/ena.c

@@ -1,5 +1,5 @@
 /*-
- * BSD LICENSE
+ * SPDX-License-Identifier: BSD-2-Clause
  *
  * Copyright (c) 2015-2020 Amazon.com, Inc. or its affiliates.
  * All rights reserved.

sys/dev/ena/ena.h

@@ -1,5 +1,5 @@
 /*-
- * BSD LICENSE
+ * SPDX-License-Identifier: BSD-2-Clause
  *
  * Copyright (c) 2015-2020 Amazon.com, Inc. or its affiliates.
  * All rights reserved.

sys/dev/ena/ena_datapath.c

@@ -1,5 +1,5 @@
 /*-
- * BSD LICENSE
+ * SPDX-License-Identifier: BSD-2-Clause
  *
  * Copyright (c) 2015-2020 Amazon.com, Inc. or its affiliates.
  * All rights reserved.

sys/dev/ena/ena_datapath.h

@@ -1,5 +1,5 @@
 /*-
- * BSD LICENSE
+ * SPDX-License-Identifier: BSD-2-Clause
  *
  * Copyright (c) 2015-2020 Amazon.com, Inc. or its affiliates.
  * All rights reserved.

sys/dev/ena/ena_netmap.c

@@ -1,5 +1,5 @@
 /*-
- * BSD LICENSE
+ * SPDX-License-Identifier: BSD-2-Clause
  *
  * Copyright (c) 2015-2020 Amazon.com, Inc. or its affiliates.
  * All rights reserved.

sys/dev/ena/ena_netmap.h

@@ -1,5 +1,5 @@
 /*-
- * BSD LICENSE
+ * SPDX-License-Identifier: BSD-2-Clause
  *
  * Copyright (c) 2015-2020 Amazon.com, Inc. or its affiliates.
  * All rights reserved.

sys/dev/ena/ena_sysctl.c

@@ -1,5 +1,5 @@
 /*-
- * BSD LICENSE
+ * SPDX-License-Identifier: BSD-2-Clause
  *
  * Copyright (c) 2015-2020 Amazon.com, Inc. or its affiliates.
  * All rights reserved.

sys/dev/ena/ena_sysctl.h

@@ -1,5 +1,5 @@
 /*-
- * BSD LICENSE
+ * SPDX-License-Identifier: BSD-2-Clause
  *
  * Copyright (c) 2015-2020 Amazon.com, Inc. or its affiliates.
  * All rights reserved.

sys/modules/ena/Makefile

@@ -1,7 +1,7 @@
 #
-# BSD LICENSE
+# SPDX-License-Identifier: BSD-2-Clause
 #
-# Copyright (c) 2015-2019 Amazon.com, Inc. or its affiliates.
+# Copyright (c) 2015-2020 Amazon.com, Inc. or its affiliates.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without