devices/ac97: keep irq event descriptors
devices/ac97: keep irq event descriptors

Fix to preserve ac97 event/resample events handles for minijail.
Broken by crrev/c/3143586

BUG=b:198773299
TEST=arcvm audio access, record/play.

Change-Id: I34d85a9f9355257c98e0c5c28e87d1e289117ed0
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3144532
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>
Reviewed-by: Kazuhiro Inaba <9f510fc648c9b290f0723164b7d6bf691fb84794@chromium.org>
Commit-Queue: Tomasz Jeznach <5b3adf4047547dabb3c4185b2cc3b12c11142cd6@chromium.org>
Commit-Queue: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>

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