Example help output (note that in main crosvm device help is broken)
```
Usage: crosvm device <command> [<args>]
Devices
Options:
--help display usage information
Commands:
block Block device
net Net device
console Console device
fs FS Device
gpu GPU device
vsock Vsock device
wl Wayland device
```
crosvm device wl help:
```
Usage: crosvm device wl --socket <PATH> --vm-socket <PATH> [--wayland-sock <PATH[,name=NAME]...>] [--resource-bridge <PATH>]
Wayland device
Options:
--socket path to bind a listening vhost-user socket
--vm-socket path to a socket for wayland-specific messages
--wayland-sock path to one or more Wayland sockets. The unnamed socket is
used for displaying virtual screens while the named ones are
used for IPC
--resource-bridge path to the GPU resource bridge
--help display usage information
```
Change-Id: Ie976b5545644c10b24cb3cdfcb17b213641064f9
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3668920
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-by: Vikram Auradkar <auradkar@google.com>
Reviewed-by: Alexandre Courbot <acourbot@chromium.org>
Commit-Queue: Anton Romanov <romanton@google.com>
