HID: hyperv: register as a wakeup source

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

This addresses part of https://bugzilla.redhat.com/show_bug.cgi?id=1086100



Signed-off-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>