io_uring: initialze sqes to zero
io_uring: initialze sqes to zero

Submission queue entries have whatever value is left from last time
stored. Clear them to zero when they are pulled out prior to being
filled. It's better to do this in a central location than making each
user responsible for setting all the fields.

Change-Id: I0436e24cd97fe4bbe808d7d0cc09fa81c1323d57
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2274995
Reviewed-by: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>
Reviewed-by: Chirantan Ekbote <35787c0e27de5c48735e07f8324823b765e8bcbc@chromium.org>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Tested-by: Dylan Reid <c791bfe44996c1eed9c7149a0c5f12a86d58eb85@chromium.org>
Commit-Queue: Dylan Reid <c791bfe44996c1eed9c7149a0c5f12a86d58eb85@chromium.org>

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