ipv6: compile fix for ip6mr.c

net/ipv6/ip6mr.c: In function 'pim6_rcv':
net/ipv6/ip6mr.c:368: error: implicit declaration of function 'csum_ipv6_magic'
Signed-off-by: NDave Jones <davej@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv6/ip6mr.c

@@ -48,6 +48,7 @@
 #include <linux/pim.h>
 #include <net/addrconf.h>
 #include <linux/netfilter_ipv6.h>
+#include <net/ip6_checksum.h>
 
 /* Big lock, protecting vif table, mrt cache and mroute socket state.
    Note that the changes are semaphored via rtnl_lock.