hasvk: Track DPB slots instead of assuming a single reference.

The encoder ignored VkVideoReferenceSlotInfoKHR entirely: it took
pReferenceSlots[0] as the one reference, wrote its address into frame store 0
and hardcoded the L0 list to that store.  Two DPB slots were all it could
honestly advertise, which is fewer than a GOP of any length needs.

Record each slot the operation names under its own index, since a slot maps
onto the frame store of the same index and MFX_PIPE_BUF_ADDR_STATE holds 16
of those, and build the L0 entries from StdVideoEncodeH264ReferenceListsInfo,
whose RefPicList0 already carries slot indices.  Clients that pass reference
slots without a list keep the old behaviour.

maxDpbSlots therefore goes to 16.  maxActiveReferencePictures stays at 1:
every macroblock is still coded against reference index 0, so a picture may
be kept in the DPB but only the one it names first is predicted from.

dEQP-VK.video.encode.h264.intra_refresh_* goes from 12 Pass and 32 stopped at
the maxDpbSlots >= GOP frame count precondition to 36 Pass, the remaining 8
being per-picture-partition mode, which is not offered.  The family as a whole
is 76 of 120 with no failures.  ffmpeg's h264_vulkan encoder no longer trips
its slot_index assertion and produces a full GOP.

Co-Authored-By: Claude Opus 5 <[email protected]>

src/intel/vulkan_hasvk/anv_genX.h

@@ -86,7 +86,8 @@ void genX(hasvk_mfc_emit_static_state)(struct anv_cmd_buffer *cmd_buffer,
                                        uint32_t dst_page_offset,
                                        uint64_t dst_buffer_range,
                                        uint32_t width_in_mbs, uint32_t height_in_mbs,
-                                       bool is_p, struct anv_address ref_address);
+                                       bool is_p,
+                                       const struct anv_video_reference_state *refs);
 
 /* Emits one slice: MFX_AVC_SLICE_STATE, the slice-header insert, the per-MB
  * PAK objects for the macroblock range [slice_start_mb, slice_end_mb), and the