vkr: move get_fence_fd to vkr_device

This is to prepare for extension cleanup and autogen.

This requires to rebase !501 (closed). Will do after this.

--- a/media-libs/virglrenderer/files/0001-vkr-add-support-for-globalFencing.patch
+++ b/media-libs/virglrenderer/files/0001-vkr-add-support-for-globalFencing.patch
@@ -232,7 +232,7 @@ index 9ac5607..c8d3a20 100644
     if (!queue)
        return -EINVAL;
     struct vkr_device *dev = queue->device;
-@@ -178,6 +201,82 @@ vkr_context_submit_fence(struct virgl_context *base,
+@@ -178,6 +201,81 @@ vkr_context_submit_fence(struct virgl_context *base,
     return ret;
  }

@@ -294,8 +294,7 @@ index 9ac5607..c8d3a20 100644
 +      .fence = sync->fence,
 +      .handleType = VK_EXTERNAL_FENCE_HANDLE_TYPE_SYNC_FD_BIT,
 +   };
-+   VkResult result =
-+      ctx->instance->get_fence_fd(dev->base.handle.device, &get_fd_info, out_fd);
++   VkResult result = dev->get_fence_fd(dev->base.handle.device, &get_fd_info, out_fd);
 +
 +   return result == VK_SUCCESS ? 0 : -1;
 +}

/cc @olv @ryanneph