Arc A380: HEVC Main (8-bit) hardware decoding not working via VAAPI

**Hardware**:
- GPU: Intel Arc A380
- Driver: intel-media-va-driver 25.2.3+dfsg1-1 (iHD_drv_video.so)
- Kernel: [aggiungi output di `uname -r`]
- OS: Debian 13 (Trixie) / LXC container

**Issue**:
HEVC Main profile (8-bit) hardware decoding is not working via VAAPI.
ffmpeg falls back to software decoder even with `-hwaccel vaapi` flag.

HEVC Main 10 profile (10-bit) works correctly with hardware acceleration.

**vainfo output**:
```
VAProfileHEVCMain : VAEntrypointVLD
VAProfileHEVCMain10 : VAEntrypointVLD
```

**Test**:
```bash
# Generate 8-bit HEVC test file
ffmpeg -f lavfi -i testsrc=duration=10:size=1920x800:rate=24 \
-c:v libx265 -preset fast -pix_fmt yuv420p test_8bit.mp4

# Try hardware decode
ffmpeg -hwaccel vaapi -hwaccel_device /dev/dri/renderD128 \
-i test_8bit.mp4 -f null -
```

**Expected**: Hardware decoder usage (vaapi surface)
**Actual**: Software fallback `hevc (native) -> wrapped_avframe`

**Note**: HEVC Main 10 (10-bit) works fine:
```bash
ffmpeg -hwaccel vaapi -hwaccel_device /dev/dri/renderD128 \
-hwaccel_output_format vaapi \
-i test_10bit.mkv -c:v av1_vaapi output.mkv
# This works perfectly with full hardware pipeline

**Request**: Please investigate HEVC Main (8-bit) decoder support for Arc A380.