[IRDA]: Remove irlan_eth_send_gratuitous_arp()

Even kernel 2.2.26 (sic) already contains the
  #undef CONFIG_IRLAN_SEND_GRATUITOUS_ARP
with the comment "but for some reason the machine crashes if you use DHCP".

Either someone finally looks into this or it's simply time to remove 
this dead code.

Reported-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/irda/irlan_eth.h

@@ -29,5 +29,4 @@ struct net_device *alloc_irlandev(const char *name);
 int  irlan_eth_receive(void *instance, void *sap, struct sk_buff *skb);
 
 void irlan_eth_flow_indication( void *instance, void *sap, LOCAL_FLOW flow);
-void irlan_eth_send_gratuitous_arp(struct net_device *dev);
 #endif