fealnx: Fix building error on MIPS

This patch try to fix the building error on MIPS. The reason is MIPS
has already defined the LONG macro, which conflicts with the LONG enum
in drivers/net/ethernet/fealnx.c.

Signed-off-by: Huacai Chen <chenhc@lemote.com>
Signed-off-by: David S. Miller <davem@davemloft.net>