Handling "connected to pc" and "connected to charger" as separate boolean
states just complicates things.

Move cable_state_t enumeration values from udev module to usb_moded.h
to make them generally available.

Utilize cable_state_t also within usb_moded.c module.
Signed-off-by: Simo Piiroinen <simo.piiroinen@jollamobile.com>