Fix some compile warnings

[francoism90]

There are a few compile warnings, maybe they don't need fixing, but I do find them annoying. :)

[nazar-pc]

I don't think it worth the effort to clean up this code. I've fixed a bunch of similar places, many of which were clearly errors by Realtek developers, but if you want to clean up codebase, you should better contribute to some actively maintained version. This repository will primarily accept updates that support newer kernels, new devices with the same chipset and not much besides that.

[francoism90]

@nazar-pc These are fixes done by aircrack-ng and others. :)

Would be great if you could merge them, think not setting the EVM value may cause issues, but I could be wrong thought.

[francoism90]

Thanks again for the merge. :)