OpenXR - Enable stereo in more games

[lvonasek]

This PR removes limitation for stereo "only if UnitsPerMeter is specified".

Let me explain why I think this is a good decision. Getting assets/compatvr.ini as a statistical coverage, I figured out:

• about 50% of games have the UnitsPerMeter = 1.0 - this is our default value
• about 40% of games have the UnitsPerMeter > 1.0 - these games will have a low stereo effect (*)
• about 10% of games have the UnitsPerMeter < 1.0 - these games will have a wrong stereo (*)

(*) when the UnitsPerMeter value isn't specified

To sum up:

• before this PR we supported stereo on about 10% of all PSP games
• after this PR we will support stereo on about 50% of all PSP games (meaing the correct stereo separation is in place)
• after this PR the stereo will be too low on 40% of all PSP games (this is not worse than than without this PR)
• after this PR the stereo will be broken on 10% of all PSP games (I will be fixing these when reported)

[hrydgard]

Yeah, this is probably a good plan. Bigger chance you'll get reports of failure cases too.