Prefer serial number from detailed descriptor over ID serial number

[pp3345]

The "ID serial number" usually isn't really useful as most vendors just fill it with some garbage value when there is also a (ASCII) serial number in one of the detailed descriptors, so prefer the latter if present. Note that many monitors only have a serial number detailed descriptor in their CTA-861 extension block which we currently don't parse, so for now we'll still display a garbage value for these monitors.

Btw, @mithro, saw you're at 35C3 too, wanna meet?

[mithro]

@pp3345 Would love to meet up! I'm at the openfpga table most of the time.

[pp3345]

@mithro Cool, will try to find you there later today