[MCAST]: Fix MCAST_EXCLUDE line dupes

This patch fixes line dupes at /ipv4/igmp.c and /ipv6/mcast.c in the  
2.6 kernel, where MCAST_EXCLUDE is mistakenly used instead of  
MCAST_INCLUDE.

Signed-off-by: Denis Lukianov <denis@voxelsoft.com>
Signed-off-by: David L Stevens <dlstevens@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>