avutil/hwcontext_vulkan: fix resource leak on alloc_mem failure

Fix by using goto fail so that vulkan_frame_free() properly cleans up
all previously created resources.

libavutil/hwcontext_vulkan.c

@@ -3568,7 +3568,7 @@ static int vulkan_map_from_drm_frame_desc(AVHWFramesContext *hwfc, AVVkFrame **f
                         &f->flags, &f->mem[i]);
         if (err) {
             close(idesc.fd);
-            return err;
+            goto fail;
         }
 
         f->size[i] = req2.memoryRequirements.size;