[Bug]: mjpeg vaapi encoder checks against 0 instead of INVALID

### Which component impacted?

Not sure

### Is it regression? Good in old configuration?

None

### What happened?

https://github.com/oneapi-src/oneVPL-intel-gpu/blob/main/_studio/mfx_lib/encode_hw/mjpeg/src/mfx_mjpeg_encode_vaapi.cpp#L531

Incorrectly checks against 0 instead of invalid, this trips debug asserts in the vaapi driver.

### What's the usage scenario when you are seeing the problem?

Others

### What impacted?

Run onVPL with debug asserts enabled in the vaapi driver and try and create a session.

### Debug Information

You can review your own h264 implementation for the proper checks.

### Do you want to contribute a patch to fix the issue?

No.