virtqueue: Re-enable notification suppression
virtqueue: Re-enable notification suppression

Now that the get and set methods have the proper memory barriers it
should be safe to re-enable this.

BUG=none
TEST=crostini.Basic.buster_stable; reboot arcvm in a loop for 75
     iterations without observing a hang

Change-Id: I03271d838e31ad091536163359836bead7e00178
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3026690
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Commit-Queue: Chirantan Ekbote <35787c0e27de5c48735e07f8324823b765e8bcbc@chromium.org>
Reviewed-by: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>

google/crosvm,google/crosvm,google/crosvm,google/crosvm