i2c: slave: Add EEPROM I2C Slave driver

Add a new EEPROM simulated driver with all it's build infrastructure.

The EEPROM can be loaded/poked from applications by getting its funcs.

It is multi-instance capable, right now 2 instances are supported by
enabling them in KConfig.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Daniel Wagenknecht <wagenknecht@clage.de>