netxen: do_rom_fast_write error handling

Compiler warning spots real error!

The function do_rom_fast_read called in do_rom_fast_write can fail
and leave data1 unset. This causes a compile warning.
The correct thing is to propagate the error out.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>