obs-ffmpeg: Fix throughput checks for older AMD driver

[rhutsAMD]

Description

This PR fixes the case where OBS does not refresh the throughput caps with the user's setting so stale throughput values are used to check preset compatibility as well as the case where ..._CAP_MAX_THROUGHPUT does not work as expected -> returns 0 -> and fails to fall back to the lowest preset.

Motivation and Context

This is a bug fix.

How Has This Been Tested?

• Tested on multiple Windows machines

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.