vulkan driver requires vsync to be OFF

First and foremost consider this:

• Only RetroArch bugs should be filed here. Not core bugs or game bugs
• This is not a forum or a help section, this is strictly developer oriented

Description

if vulkan is driver and vsync is on, you get stuttering A/V, FULLSCREEN only, does not affect windowed

Expected behavior

smooth A/V

Actual behavior

framrate drops below core norm or resolution norm in RA UI

Steps to reproduce the bug

1. set vulkan as driver
2. make sure vsync is on
3. start a core that uses vulkan (beetle psx, parallel, etc..)
4. observer performance in full screen (bug does not affect windowed)
5. turn vsync off and observe difference in performance

Bisect Results

[Try to bisect and tell us when this started happening]

Version/Commit

You can find this information under Information/System Information

• RetroArch: 1.8.7

Environment information

• OS: windows 10 pro 64bit, gtx 1660, latest nvidia drivers
• Compiler: [In case you are running local builds]

Reproduce the issue using the listed Windows 10, GTX 1660, fullscreen Vulkan, and vsync settings, comparing performance with vsync enabled and disabled. Narrow the regression with a bisect if possible; done means smooth audio/video in fullscreen with vsync enabled while windowed behavior remains unchanged.