icstation-usbrelay: Initial ICStation USBRelay driver.

icstation-usbrelay: Initial ICStation USBRelay driver.

Implement support for several ICStation USBRelay models with 2, 4, and 8
channels. Allows to identify the cards after power-on, and subsequent
relay control.

IMPORTANT: An implementation detail in the vendor firmware prevents the
host application from identifying the device after entering command mode.
Identification will fail, and the identification request instead gets
mistaken for another relay control request (turns on relays 1-4, 6, 8).
A power cycle is required before the host application can reconnect to
the device.