ax88796: add 93cx6 eeprom support

Hook up the 93cx6 eeprom code to the ax88796 driver and modify the ax88796
driver to read out the mac address from the eeprom.  We need this for the
ax88796 on certain SuperH boards.  The pin configuration used to connect
the eeprom to the ax88796 on these boards is the same as pointed out by the
ax88796 datasheet, so we can probably reuse this code for multiple
platforms in the future.

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Cc: Ben Dooks <ben-linux@fluff.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>