net: dsa/mv88e6352: Implement EEPROM access functions

MV88E6352 supports read and write access to its configuration eeprom.

There is no means to detect if an EEPROM is connected to the switch.
Also, the switch supports EEPROMs with different sizes, but can not detect
or report the type or size of connected EEPROMs. Therefore, do not implement
the get_eeprom_len callback but depend on platform or devicetree data to
provide information about EEPROM presence and size.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: David S. Miller <davem@davemloft.net>