[LLC]: multicast receive device match

Fix from Aji_Srinivas@emc.com, STP packets are incorrectly received on
all LLC datagram sockets, whichever interface they are bound to.  The
llc_sap datagram receive logic sends packets with a unicast
destination MAC to one socket bound to that SAP and MAC, and multicast
packets to all sockets bound to that SAP. STP packets are multicast,
and we do need to know on which interface they were received.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>