meta-google: ipmi-fru-sh: Add method for initializing eeproms

This makes it possible to create new specifications besides the default
mapping of OF name to eeprom path. Right now this provides backward
compatability with anything that uses of_name_to_eeprom and only
provides a new explicit specifier for that specification.

Change-Id: If02d9cb392a48e0698b10644d7ade3220bde3eb5
Signed-off-by: William A. Kennington III <wak@google.com>