usbkm: Make emulator wake capable.

This patch helps us make the kb emulator in the servo wake capable.
This helps us in testing wakes from usb hid devices.
Changes involve
     1. Changing the configuration descriptor to advertise the emulator
     as wake capable.
     2. Triggering remote wake signal if the operating system has asked
     to do so.
     3. Fix few compile time issues.

BUG=chromium:820668
TEST=flashed the kb emulator and tested it can wake the system up.

Change-Id: I02bd8d376145e5674abc0533d59d25bd1f3dad10
Reviewed-on: https://chromium-review.googlesource.com/1175001
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Ravi Chandra Sadineni <ravisadineni@chromium.org>
Reviewed-by: Nick Sanders <nsanders@chromium.org>
Reviewed-by: Todd Broch <tbroch@chromium.org>
4 files changed