Fix crash issue on latest nvidia windows drivers

[smurfy]

Latest windows nvidia drivers do not ship opencl drivers with them anymore. Which causes hwmon to crash enumerating ocl platforms.

This PR is against 0.17, but i can change that if needed.

Resolves #1841

[AndreaLanfranchi]

What if you launch with -U ?
It should completely bypass OpenCL detection

[smurfy]

What if you launch with -U ?
It should completely bypass OpenCL detection

does not help, as you see in the code, nvml wrapper will call opencl methods to create its mapping.
cl::Platform::get(&platforms); causes an exception to be thrown if no platform is detected.

My changes fixes that.

edit: only thing which will "help" is if its compiled without opencl support at all :)

[AndreaLanfranchi]

Ok. I see the point.

[smurfy]

Is target branch ok or should i do it agains master?

[AndreaLanfranchi]

@smurfy the branch is ok.
Latest master does not have this problem anymore as wrapnvml.cpp has been modified to not require any correspondence by card id. It does it directly with PCI id.
Hopefully @chfast will release 0.18 anytime soon.

[chfast]

This fix is not needed in the master branch? I cannot find this piece of code.

[AndreaLanfranchi]

@chfast
not needed. Read my earlier comment.