frontends/va: Fix leaks with multiple coded buffer segments

The buffers can be reused, so we must only allocate added segments
and free unused segments.

Fixes: be4287c3aa ("pipe: Extend get_feedback with additional metadata")
Reviewed-By: Sil Vilerino <sivileri@microsoft.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30779>

src/gallium/frontends/va/buffer.c

@@ -216,11 +216,20 @@ VAStatus vlVaMapBuffer2(VADriverContextP ctx, VABufferID buf_id,
             *pbuff = buf->data;
 
             for (size_t i = 0; i < buf->extended_metadata.codec_unit_metadata_count - 1; i++) {
-               curr_buf_ptr->next = CALLOC(1, sizeof(VACodedBufferSegment));
+               if (!curr_buf_ptr->next)
+                  curr_buf_ptr->next = CALLOC(1, sizeof(VACodedBufferSegment));
                if (!curr_buf_ptr->next)
                   return VA_STATUS_ERROR_ALLOCATION_FAILED;
                curr_buf_ptr = curr_buf_ptr->next;
             }
+            if (curr_buf_ptr->next) {
+               VACodedBufferSegment *node = curr_buf_ptr->next;
+               while (node) {
+                  VACodedBufferSegment *next = node->next;
+                  FREE(node);
+                  node = next;
+               }
+            }
             curr_buf_ptr->next = NULL;
 
             curr_buf_ptr = buf->data;