HID: usbhid: base runtime PM on modern API

This patch doesn't alter functionality, but removes a dedicated kernel
thread.

Signed-off-by: Oliver Neukum <oneukum@suse.de>
Tested-by: Maulik Mankad <x0082077@ti.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>