atm: firestream: remove duplicate define

This patch removes a duplicate define in drivers/atm/firestream.h

Signed-off-by: Michael Opdenacker <michael.opdenacker@free-electrons.com>
Acked-by: Chas Williams <chas@cmf.nrl.navy.mil>
Signed-off-by: David S. Miller <davem@davemloft.net>