Reapply "virtio-blk: don't keep queue frozen during system suspend"

This reverts commit cd645a42.

Turns out this is not a runtime breakage, but rather just a missing
symbol.  Add back the change as this should be just fine.

Change-Id: Ib109c5533c66d74ea45e6f05c59f96da64d6cc80
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>