Incorporated review comments from Ben Hutchings.

Change details:
	- Implement ethtool flash_device() entry point to write the
	  firmware image to the flash firmware partition.
Signed-off-by: NKrishna Gudipati <kgudipat@brocade.com>
Reviewed-by: NBen Hutchings <bhutchings@solarflare.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>