Add SPDX license info (#265)

Signed-off-by: Alan Jowett <alanjo@microsoft.com>
diff --git a/vm/Makefile b/vm/Makefile
index e202629..86d139f 100644
--- a/vm/Makefile
+++ b/vm/Makefile
@@ -1,3 +1,6 @@
+# Copyright (c) 2015 Big Switch Networks, Inc
+# SPDX-License-Identifier: Apache-2.0
+
 # Copyright 2015 Big Switch Networks, Inc
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
diff --git a/vm/compat/macos/endian.h b/vm/compat/macos/endian.h
index 0af1ea4..b9fb98e 100644
--- a/vm/compat/macos/endian.h
+++ b/vm/compat/macos/endian.h
@@ -1,3 +1,6 @@
+// Copyright (c) 2022 IO Visor Project
+// SPDX-License-Identifier: Apache-2.0
+
 /*
   Copyright (c) 2022-present, IO Visor Project
   All rights reserved.
diff --git a/vm/compat/windows/endian.h b/vm/compat/windows/endian.h
index 5f1dcf0..30484bb 100644
--- a/vm/compat/windows/endian.h
+++ b/vm/compat/windows/endian.h
@@ -1,3 +1,6 @@
+// Copyright (c) 2022 IO Visor Project

+// SPDX-License-Identifier: Apache-2.0

+

 /*

   Copyright (c) 2022-present, IO Visor Project

   All rights reserved.

diff --git a/vm/compat/windows/sys/mman.h b/vm/compat/windows/sys/mman.h
index 7482b37..cc85afb 100644
--- a/vm/compat/windows/sys/mman.h
+++ b/vm/compat/windows/sys/mman.h
@@ -1,3 +1,6 @@
+// Copyright (c) 2022 IO Visor Project

+// SPDX-License-Identifier: Apache-2.0

+

 /*

   Copyright (c) 2022-present, IO Visor Project

   All rights reserved.

diff --git a/vm/compat/windows/unistd.c b/vm/compat/windows/unistd.c
index 8096c8f..a0a82b4 100644
--- a/vm/compat/windows/unistd.c
+++ b/vm/compat/windows/unistd.c
@@ -1,3 +1,6 @@
+// Copyright (c) 2022 IO Visor Project

+// SPDX-License-Identifier: Apache-2.0

+

 /*

   Copyright (c) 2022-present, IO Visor Project

   All rights reserved.

diff --git a/vm/compat/windows/unistd.h b/vm/compat/windows/unistd.h
index 1f8110a..09de2a6 100644
--- a/vm/compat/windows/unistd.h
+++ b/vm/compat/windows/unistd.h
@@ -1,3 +1,6 @@
+// Copyright (c) 2022 IO Visor Project

+// SPDX-License-Identifier: Apache-2.0

+

 /*

   Copyright (c) 2022-present, IO Visor Project

   All rights reserved.

diff --git a/vm/ebpf.h b/vm/ebpf.h
index e9725a3..52af1f7 100644
--- a/vm/ebpf.h
+++ b/vm/ebpf.h
@@ -1,3 +1,6 @@
+// Copyright (c) 2015 Big Switch Networks, Inc
+// SPDX-License-Identifier: Apache-2.0
+
 /*
  * Copyright 2015 Big Switch Networks, Inc
  *
diff --git a/vm/ubpf_jit_arm64.c b/vm/ubpf_jit_arm64.c
index 42edcec..de62f07 100644
--- a/vm/ubpf_jit_arm64.c
+++ b/vm/ubpf_jit_arm64.c
@@ -1,3 +1,6 @@
+// Copyright (c) 2015 Big Switch Networks, Inc
+// SPDX-License-Identifier: Apache-2.0
+
 /*
  * Copyright 2015 Big Switch Networks, Inc
  * Copyright 2017 Google Inc.
diff --git a/vm/ubpf_jit_x86_64.c b/vm/ubpf_jit_x86_64.c
index 7e68ad9..196d285 100644
--- a/vm/ubpf_jit_x86_64.c
+++ b/vm/ubpf_jit_x86_64.c
@@ -1,3 +1,6 @@
+// Copyright (c) 2015 Big Switch Networks, Inc
+// SPDX-License-Identifier: Apache-2.0
+
 /*
  * Copyright 2015 Big Switch Networks, Inc
  * Copyright 2017 Google Inc.
diff --git a/vm/ubpf_jit_x86_64.h b/vm/ubpf_jit_x86_64.h
index 24727a0..c63fdd5 100644
--- a/vm/ubpf_jit_x86_64.h
+++ b/vm/ubpf_jit_x86_64.h
@@ -1,3 +1,6 @@
+// Copyright (c) 2015 Big Switch Networks, Inc
+// SPDX-License-Identifier: Apache-2.0
+
 /*
  * Copyright 2015 Big Switch Networks, Inc
  *