Add ability to query size of eeprom device and partitions

Signed-off-by: Robert Beckett <bob.beckett@collabora.com>
Series-to: u-boot@lists.denx.de
Series-cc: Robert Beckett <bob.beckett@collabora.com>
Cover-letter:
misc: i2c_eeprom: add paritioning and size query
Add ability to specify paritions for eeprom in device tree, and query
eeprom device sizes.
Each partition creates a child device, allowing board code to
find the eeprom parition by name.
END