e1000: Fix driver to be used on PA RISC C8000 workstations

The checksum field in the EEPROM on HPPA is really not a
checksum but a signature (0x16d6).  So allow 0x16d6 as the
matching checksum on HPPA systems.

This issue is present on longterm/stable kernels, I have
verified that this patch is applicable back to at least
2.6.32.y kernels.

v2- changed ifdef to use CONFIG_PARISC instead of __hppa__

CC: Guy Martin <gmsoft@tuxicoman.be>
CC: Rolf Eike Beer <eike-kernel@sf-tec.de>
CC: Matt Turner <mattst88@gmail.com>
Reported-by: Mikulas Patocka <mikulas@artax.kerlin.mff.cuni.cz>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Acked-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>