ANDROID: add blk_mq_freeze_queue and blk_mq_unfreeze_queue to virtual device symbol list

In commit 2a52590a ("virtio-blk: Ensure no requests in virtqueues
before deleting vqs.") the virtio_blk driver adds calls to
blk_mq_freeze_queue and blk_mq_unfreeze_queue, so add them to the
virtual device symbol list so that that target will build properly.

Fixes: 2a52590a ("virtio-blk: Ensure no requests in virtqueues before deleting vqs.")
Change-Id: Iaf7ef825414a5bc3db36cd9479acb0c1a7435e11
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>