net/ipv6/sit.c: Checkpatch cleanup

sit.c:118: ERROR: "foo * bar" should be "foo *bar"
sit.c:694: ERROR: "(foo*)" should be "(foo *)"
sit.c:724: ERROR: "(foo*)" should be "(foo *)"

Signed-off-by: Eldad Zack <eldad@fogrefinery.com>
Signed-off-by: David S. Miller <davem@davemloft.net>