linux: Drop workaround for kernel < 2.6.34

[z3ntu]

Also drop HIDIOC* definitions as they are present since kernel 2.6.39.

[Youw]

where do we define minimum supported kernel?

[z3ntu]

Nowhere as far as I know. But I guess everything above 2.6.39 should work now, but I haven't tested that. And as this version is so old, I don't think it's necessary to document this as it should *just work* on any halfway recent Linux kernel.

[Youw]

I still think it worth adding at least README notice. Would you?

[z3ntu]

If you're willing to test hidapi on e.g. kernel 2.6.39 then sure; but other than downloading the oldest supported CentOS version (disclaimer: I just know that they have super old kernels but I have no idea what version) I wouldn't even know how to get a VM running kernel 2.6.39

[Youw]

Hm, good point - don't want to check/make any assures on support.
What about:
"Don't try to compile with Kernel older than 2.6.39 - it won't".

As usual, there will be that one person, who will try and open a bug.

[z3ntu]

As usual, there will be that one person, who will try and open a bug.

I'd say, if someone opens a bug report for that, we can add it to the readme 😉