It shouldn't happen, but can happen that readable eeprom size is smaller
than announced. Then we would be stuck in an endless loop here because
after reaching the actual end reads return eeprom.len = 0. I faced this
issue when making a mistake in driver development. Detect this scenario
and return an error.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>