l2tp: Fix spelling mistakes

Fix some spelling mistakes in comments:
negociated  ==> negotiated
dont  ==> don't
Signed-off-by: Zheng Yongjun <zhengyongjun3@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/l2tp/l2tp_ip.c

@@ -488,7 +488,7 @@ static int l2tp_ip_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 		}
 	}
 
-	/* We dont need to clone dst here, it is guaranteed to not disappear.
+	/* We don't need to clone dst here, it is guaranteed to not disappear.
 	 *  __dev_xmit_skb() might force a refcount if needed.
 	 */
 	skb_dst_set_noref(skb, &rt->dst);

net/l2tp/l2tp_ppp.c

@@ -226,7 +226,7 @@ static void pppol2tp_recv(struct l2tp_session *session, struct sk_buff *skb, int
 	/* If the first two bytes are 0xFF03, consider that it is the PPP's
 	 * Address and Control fields and skip them. The L2TP module has always
 	 * worked this way, although, in theory, the use of these fields should
-	 * be negociated and handled at the PPP layer. These fields are
+	 * be negotiated and handled at the PPP layer. These fields are
 	 * constant: 0xFF is the All-Stations Address and 0x03 the Unnumbered
 	 * Information command with Poll/Final bit set to zero (RFC 1662).
 	 */