net: Fix bug in compat SIOCGETSGCNT handling.

Commit 709b46e8 ("net: Add compat
ioctl support for the ipv4 multicast ioctl SIOCGETSGCNT") added the
correct plumbing to handle SIOCGETSGCNT properly.

However, whilst definiting a proper "struct compat_sioc_sg_req" it
isn't actually used in ipmr_compat_ioctl().

Correct this oversight.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/ipmr.c

@@ -1446,7 +1446,7 @@ struct compat_sioc_sg_req {
 
 int ipmr_compat_ioctl(struct sock *sk, unsigned int cmd, void __user *arg)
 {
-	struct sioc_sg_req sr;
+	struct compat_sioc_sg_req sr;
 	struct mfc_cache *c;
 	struct net *net = sock_net(sk);
 	struct mr_table *mrt;