BBAPI on Linux 5.15

[jeremymika]

If you are here, you already know that BBAPI does not easily build for kernels >= 5.8, per the README from Beckhoff.

I have been able to build for 5.15, and want to share what I did in hopes that it helps others.

NOTE: I did not make sure this compiled for earlier kernels, though that should not be difficult.