hwcontext_vulkan: check for non-flagged transfer queue families

"All commands that are allowed on a queue that supports transfer
operations are also allowed on a queue that supports either
graphics or compute operations. Thus, if the capabilities of a
queue family include VK_QUEUE_GRAPHICS_BIT or VK_QUEUE_COMPUTE_BIT,
then reporting the VK_QUEUE_TRANSFER_BIT capability separately for
that queue family is optional."

libavutil/hwcontext_vulkan.c

@@ -832,6 +832,13 @@ static int setup_queue_families(AVHWDeviceContext *ctx, VkDeviceCreateInfo *cd)
     enc_index   = pick_queue_family(qf, num, VK_QUEUE_VIDEO_ENCODE_BIT_KHR);
     dec_index   = pick_queue_family(qf, num, VK_QUEUE_VIDEO_DECODE_BIT_KHR);
 
+    /* Signalling the transfer capabilities on a queue family is optional */
+    if (tx_index < 0) {
+        tx_index = pick_queue_family(qf, num, VK_QUEUE_COMPUTE_BIT);
+        if (tx_index < 0)
+            tx_index = pick_queue_family(qf, num, VK_QUEUE_GRAPHICS_BIT);
+    }
+
     hwctx->queue_family_index        = -1;
     hwctx->queue_family_comp_index   = -1;
     hwctx->queue_family_tx_index     = -1;