net: ne2000: Divided a function of NE2000 driver

get_prom function was used __attriute__ , but it is not enable.
ax88796.o does not do link besides ne2000.o. When ld is carried
out, get_prom function of ax88796.c is ignored.
This problem is a thing by specifications of ld.
I checked and test this patch on SuperH and MIPS.

Signed-off-by: Nobuhiro Iwamatsu <iwamatsu.nobuhiro@renesas.com>
Signed-off-by: Ben Warren <biggerbadderben@gmail.com>