Input: hyperv-keyboard - register as a wakeup source

With this patch, we can press a key to wake up the VM after the VM executes
"echo freeze > /sys/power/state".

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>