Power: Reset: Generalize qnap-poweroff to work on Synology devices.

The Synology NAS devices use a very similar mechanism to QNAP NAS
devices to power off. Both send a single charactor command to a PIC,
over the second serial port. However the baud rate and the command
differ. Generalize the driver to support this.

Signed-off-by: Ben Peddell <klightspeed@killerwolves.net>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Jason Cooper <jason@lakedaemon.net>
Cc: Anton Vorontsov <anton@enomsg.org>
Cc: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>