drivers/misc: Add basic support for ATSHA204A Crypto module

This module can be found on the Turris Omnia board connected
via the I2C interface.

Among some cryptographic functions, the chip has a 512 bit
One Time Programmable memory, 88 byte configuration memory
and 512 byte general purpose memory.

The Turris Omnia stores serial number and device MAC address in
the OTP memory.

This commit adds basic support for reading the EEPROM and also
exposes the chips Random Number Generator.

The driver is based on code by
  Josh Datko, Cryptotronix, jbd@cryptotronix.com
and also
  Tomas Hlavacek, CZ.NIC, tomas.hlavacek@nic.cz

Signed-off-by: Tomas Hlavacek <tomas.hlavacek@nic.cz>
Signed-off-by: Marek Behun <marek.behun@nic.cz>

 create mode 100644 drivers/misc/atsha204a-i2c.c
 create mode 100644 include/atsha204a-i2c.h
Signed-off-by: Stefan Roese <sr@denx.de>