ipv6: fix array index in ip6_mc_add_src()

Convert array index from the loop bound to the loop index.

And remove the void type conversion to ip6_mc_del1_src() return
code, seem it is unnecessary, since ip6_mc_del1_src() does not
use __must_check similar attribute, no compiler will report the
warning when it is removed.

v2: enrich the commit header
Signed-off-by: RongQing.Li <roy.qing.li@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/mcast.c

@@ -2044,7 +2044,7 @@ static int ip6_mc_add_src(struct inet6_dev *idev, const struct in6_addr *pmca,
 		if (!delta)
 			pmc->mca_sfcount[sfmode]--;
 		for (j=0; j<i; j++)
-			(void) ip6_mc_del1_src(pmc, sfmode, &psfsrc[i]);
+			ip6_mc_del1_src(pmc, sfmode, &psfsrc[j]);
 	} else if (isexclude != (pmc->mca_sfcount[MCAST_EXCLUDE] != 0)) {
 		struct ip6_sf_list *psf;