Add license header to top of all code files

[tgorochowik]

Fixes #749

[mithro]

Bunch of comments.

Please go through the checklist at f4pga/ideas#47 and confirm that everything in it has been done for this CL, then rerequest review.

[tgorochowik]

A copy from the original task to track progress here:

• COPYING file renamed to LICENSE file
• The LICENSE file should start with - Copyright 20XX The [Project Name] Authors. -- See https://opensource.google/docs/releasing/authors/
• Add or update the AUTHORS files to have the text as shown at https://opensource.google/docs/releasing/authors/
• Remove the un-needed All rights reserved. text.
• Make sure all code files have the license specifier at the top of the file as shown at https://opensource.google/docs/releasing/licenses/
• All code files should have SPDX identifiers.
• Add CI which checks for all this.
• Make sure that all third_party code is under third_party directory.
• Make sure that all third_party directories have a correct LICENSE file.
• Python files should have a #!/usr/bin/env python3 as the shebang line.
• Python files should have a # coding: utf-8 as the second line after the shebang.

[tgorochowik]

@mithro thanks for your comments.

The only thing that is missing from the list in f4pga/ideas#47 is the CI to check for all of this. I guess this should be something common for all the repositories. Do we have something like that somewhere already?

[kgugala]

@mithro thanks for your comments.

The only thing that is missing from the list in SymbiFlow/ideas#47 is the CI to check for all of this. I guess this should be something common for all the repositories. Do we have something like that somewhere already?

@tgorochowik, @acomodi added a script for checking this in this PR chipsalliance/fpga-tool-perf#64

[tgorochowik]

Added the license checker by @acomodi from #773

[hzeller]

What is the status of this one ? It requires rebasing, but other than that, is @mithro happy ?

[tgorochowik]

Rebased the changes onto current master. All the requirements are met so I think this is ready (assuming the CI succeeds).

[mithro]

@tgorochowik -- Can you rebase this and we can merge it?

[mithro]

Can you rebase this and update the scripts from the copies in python-symbiflow-v2x - then please ping me and I'll merge it.

[mithro]

One minor fix;

ERROR: third_party/cores/black-parrot does not have the LICENSE file.
ERROR: third_party/tests/axi_vip does not have the LICENSE file.
Error: Process completed with exit code 1.