[Bug]: No multi reference frames(>2) supported on DG2

### Which component impacted?

Encode

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

None

### What happened?

1. Linux OS
2. use gmmlib/media-driver/onevpl gitbub master commit.
3. Run ffmpeg-qsv cmd with multi reference frames(>2)(set with option `-refs 3`), but the output frames in bitstream only use 2 reference frame at most.
3.1 AVC encode:
ffmpeg -v verbose -hwaccel qsv -hwaccel_output_format qsv -f lavfi -i testsrc=size=1280x720 -vf 'format=nv12,hwupload=extra_hw_frames=120' -c:v h264_qsv -refs 3 -rc_mode cqp -q 10 -b_strategy 0 -vframes 100 -y qsv.mp4
3.2 HEVC encode:
ffmpeg -v verbose -hwaccel qsv -hwaccel_output_format qsv -f lavfi -i testsrc=size=1280x720 -vf 'format=nv12,hwupload=extra_hw_frames=120' -c:v hevc_qsv -refs 3 -rc_mode cqp -q 10 -b_strategy 0 -vframes 100 -y qsv.mp4
3.3 AV1 encode:
ffmpeg -v verbose -hwaccel qsv -hwaccel_output_format qsv -f lavfi -i testsrc=size=1280x720 -vf 'format=nv12,hwupload=extra_hw_frames=120' -c:v av1_qsv -refs 3 -rc_mode cqp -q 10 -b_strategy 0 -vframes 100 -y qsv.mp4
4. While `vainfo -a` shows that AVC/HEVC/AV1 can support more than 2 reference frames. And same cmd on TGL looks good.

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

Transcode for media delivery

### What impacted?

_No response_

### Debug Information

_No response_

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

None