[802.11] Support multicast hashing

802.11 multicast hashing is the same as standard Ethernet hashing, so
just expose and use eth_mc_hash().

Signed-off-by: Joshua Oreman <oremanj@rwcr.net>

src/include/gpxe/ethernet.h

@@ -13,6 +13,8 @@ FILE_LICENCE ( GPL2_OR_LATER );
 
 extern void eth_init_addr ( const void *hw_addr, void *ll_addr );
 extern const char * eth_ntoa ( const void *ll_addr );
+extern int eth_mc_hash ( unsigned int af, const void *net_addr,
+			 void *ll_addr );
 extern struct net_device * alloc_etherdev ( size_t priv_size );
 
 #endif /* _GPXE_ETHERNET_H */