[ETHTOOL]: Add support for large eeproms

Currently, it is not possible to read/write to an eeprom larger than
128k in size because the buffer used for temporarily storing the
eeprom contents is allocated using kmalloc. kmalloc can only allocate
a maximum of 128k depending on architecture.

Modified ethtool_get/set_eeprom to only allocate a page of memory and
then copy the eeprom a page at a time.

Updated original patch as per suggestions from Joe Perches.

Signed-off-by: Mandeep Singh Baines <msb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>