USB: full autosuspend and power management support for usbsevseg

This patch adds to the usbsevseg driver:

- suspend/resume support
- reset_resume support
- autosuspend using the display's power state to determine idleness

Signed-off-by: Oliver Neukum <oliver@neukum.org>
Signed-off-by: Harrison Metzger <harrisonmetz@gmail.com>