vaapi: bump vaapi info callback to verbose messages

The info provided for libva might be useful. Specifically on Windows it
seems to not use the error callback for what should be logged as error.

[   0.080][v][vaapi] libva: VA-API version 1.20.0
[   0.080][v][vaapi] libva: Trying to open <path>/vaon12_drv_video.dll
[   0.080][v][vaapi] libva: va_openDriver() returns -1
[   0.080][e][vaapi] Failed to initialize VAAPI: unknown libva error

As we can see only the "unknown" error is printed to the error callback
and important information is printed on the info callback. Print it to
verbose log to make it easier to find.