test: Fix speling issues

Found by codespell

test/fuzz/fuzz_common.c

@@ -267,7 +267,7 @@ static void input_pkts(enum lwip_fuzz_type type, struct netif *netif, const u8_t
 #if LWIP_TCP
 static struct altcp_pcb *tcp_client_pcb;  /* a pcb for the TCP client */
 static struct altcp_pcb *tcp_server_pcb;  /* a pcb for the TCP server */
-static u16_t            tcp_remote_port;  /* a TCP port number of the destionation */
+static u16_t            tcp_remote_port;  /* a TCP port number of the destination */
 static u16_t            tcp_local_port;   /* a TCP port number of the local server */
 
 /**
@@ -519,7 +519,7 @@ udp_app_fuzz_input(struct udp_pcb *pcb, const ip_addr_t *addr, u16_t port)
        *     We use udp_send().
        *
        * server:
-       *     The pcb does NOT have infomation about the destionation.
+       *     The pcb does NOT have information about the destination.
        *     We use udp_sendto().
        */
       if (addr == NULL) {

test/unit/api/test_sockets.c

@@ -252,7 +252,7 @@ static void test_sockets_msgapi_update_iovs(struct msghdr *msg, size_t bytes)
 {
   msg_iovlen_t i;
 
-  /* note: this modifies the underyling iov_base and iov_len for a partial
+  /* note: this modifies the underlying iov_base and iov_len for a partial
      read for an individual vector. This updates the msg->msg_iov pointer
      to skip fully consumed vectors */
   

test/unit/tcp/test_tcp.c

@@ -517,7 +517,7 @@ START_TEST(test_tcp_fast_retx_recover)
   /* queue data4, don't send it (unsent-oversize is != 0) */
   err = tcp_write(pcb, data4, sizeof(data4), TCP_WRITE_FLAG_COPY);
   EXPECT_RET(err == ERR_OK);
-  /* 3nd duplicate ACK for data1 (data2 and data3 are lost) -> fast retransmission */
+  /* 3rd duplicate ACK for data1 (data2 and data3 are lost) -> fast retransmission */
   p = tcp_create_rx_segment(pcb, NULL, 0, 0, 0, TCP_ACK);
   EXPECT_RET(p != NULL);
   test_tcp_input(p, &netif);

test/unit/tcp/test_tcp_oos.c

@@ -515,7 +515,7 @@ START_TEST(test_tcp_recv_ooseq_overrun_rxwin)
     }
   }
 
-  /* pass in one more segment, cleary overrunning the rxwin */
+  /* pass in one more segment, clearly overrunning the rxwin */
   p_ovr = tcp_create_rx_segment(pcb, &data_full_wnd[TCP_MSS*(k+1)], TCP_MSS, TCP_MSS*(k+1), 0, TCP_ACK);
   EXPECT_RET(p_ovr != NULL);
   /* pass the segment to tcp_input */
@@ -602,7 +602,7 @@ START_TEST(test_tcp_recv_ooseq_overrun_rxwin_edge)
     }
   }
 
-  /* pass in one more segment, cleary overrunning the rxwin */
+  /* pass in one more segment, clearly overrunning the rxwin */
   p_ovr = tcp_create_rx_segment(pcb, &data_full_wnd[TCP_MSS*(k+1)], TCP_MSS, TCP_MSS*(k+1), 0, TCP_ACK);
   EXPECT_RET(p_ovr != NULL);
   /* pass the segment to tcp_input */