arm: mvebu: turris_mox: Read info (and ethaddrs) from OTP

Add support for reading One-Time Programmable memory via mailbox, which
communicates with CZ.NIC's firmware on the Secure Processor (Cortex-M3)
of Armada 3720.

Display product serial number and additional info, and also set MAC
addresses.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Stefan Roese <sr@denx.de>
Signed-off-by: Stefan Roese <sr@denx.de>