[E100]: Add module option to ignore bad EEPROM checksums.

Several people run into the situation where the E100
EEPROM contents are fine, but the checksum hasn't been
set properly.  This renders the device useless for
them even though it would function correctly.

The default is off, which retains the current behavior.

Signed-off-by: David S. Miller <davem@davemloft.net>