hwcontext_vulkan: improve queue family init code

When users zero-init'd the struct, or left it as-is, the encode
queue family matched the graphics queue family, which led it to be
incorrectly logged as being used for encode.

This just improves the logging so this isn't printed anymore.

libavutil/hwcontext_vulkan.c

@@ -1475,11 +1475,11 @@ static int vulkan_device_init(AVHWDeviceContext *ctx)
 
     av_free(qf);
 
-    graph_index = hwctx->queue_family_index;
-    comp_index  = hwctx->queue_family_comp_index;
-    tx_index    = hwctx->queue_family_tx_index;
-    enc_index   = hwctx->queue_family_encode_index;
-    dec_index   = hwctx->queue_family_decode_index;
+    graph_index = hwctx->nb_graphics_queues ? hwctx->queue_family_index : -1;
+    comp_index  = hwctx->nb_comp_queues ? hwctx->queue_family_comp_index : -1;
+    tx_index    = hwctx->nb_tx_queues ? hwctx->queue_family_tx_index : -1;
+    dec_index   = hwctx->nb_decode_queues ? hwctx->queue_family_decode_index : -1;
+    enc_index   = hwctx->nb_encode_queues ? hwctx->queue_family_encode_index : -1;
 
 #define CHECK_QUEUE(type, required, fidx, ctx_qf, qc)                                           \
     do {                                                                                        \
@@ -1512,10 +1512,10 @@ static int vulkan_device_init(AVHWDeviceContext *ctx)
     } while (0)
 
     CHECK_QUEUE("graphics", 0, graph_index, hwctx->queue_family_index,        hwctx->nb_graphics_queues);
-    CHECK_QUEUE("upload",   1, tx_index,    hwctx->queue_family_tx_index,     hwctx->nb_tx_queues);
     CHECK_QUEUE("compute",  1, comp_index,  hwctx->queue_family_comp_index,   hwctx->nb_comp_queues);
-    CHECK_QUEUE("encode",   0, enc_index,   hwctx->queue_family_encode_index, hwctx->nb_encode_queues);
+    CHECK_QUEUE("upload",   1, tx_index,    hwctx->queue_family_tx_index,     hwctx->nb_tx_queues);
     CHECK_QUEUE("decode",   0, dec_index,   hwctx->queue_family_decode_index, hwctx->nb_decode_queues);
+    CHECK_QUEUE("encode",   0, enc_index,   hwctx->queue_family_encode_index, hwctx->nb_encode_queues);
 
 #undef CHECK_QUEUE