wl: increase max FDs to send/recv

This change is to support a related kernel change but is backwards
compatible with kernels without that change.

BUG=chromium:782474
TEST=None

Change-Id: Ic1224b65ed9685f246002f946cfc6bfa2dbb2856
Reviewed-on: https://chromium-review.googlesource.com/770593
Commit-Ready: Zach Reizner <zachr@chromium.org>
Tested-by: Zach Reizner <zachr@chromium.org>
Reviewed-by: Stephen Barber <smbarber@chromium.org>
diff --git a/devices/src/virtio/wl.rs b/devices/src/virtio/wl.rs
index c5a67d7..71fa80a 100644
--- a/devices/src/virtio/wl.rs
+++ b/devices/src/virtio/wl.rs
@@ -55,7 +55,7 @@
 use vm_control::{VmControlError, VmRequest, VmResponse, MaybeOwnedFd};
 use super::{VirtioDevice, Queue, DescriptorChain, INTERRUPT_STATUS_USED_RING, TYPE_WL};
 
-const VIRTWL_SEND_MAX_ALLOCS: usize = 16;
+const VIRTWL_SEND_MAX_ALLOCS: usize = 28;
 const VIRTIO_WL_CMD_VFD_NEW: u32 = 256;
 const VIRTIO_WL_CMD_VFD_CLOSE: u32 = 257;
 const VIRTIO_WL_CMD_VFD_SEND: u32 = 258;