io_uring: Don't set the num_wait value during submit
io_uring: Don't set the num_wait value during submit

The value is ignored if WAIT isn't indicated in the flags, but it's more
clear what is happening if left as zero as well.

Change-Id: Ib3539e37d1eaad6f5a68f6c028cdd186f12a8dd4
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2274994
Reviewed-by: Chirantan Ekbote <35787c0e27de5c48735e07f8324823b765e8bcbc@chromium.org>
Reviewed-by: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>
Tested-by: Dylan Reid <c791bfe44996c1eed9c7149a0c5f12a86d58eb85@chromium.org>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Commit-Queue: Dylan Reid <c791bfe44996c1eed9c7149a0c5f12a86d58eb85@chromium.org>

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