style: fix spelling in code comments and strings

net/sixlowpan/sixlowpan.h

@@ -98,7 +98,7 @@ ssize_t psock_6lowpan_tcp_send(FAR struct socket *psock, FAR const void *buf,
  * Name: sixlowpan_tcp_send
  *
  * Description:
- *   TCP output comes through three different mechansims.  Either from:
+ *   TCP output comes through three different mechanisms.  Either from:
  *
  *   1. TCP socket output.  For the case of TCP output to an
  *      IEEE802.15.4, the TCP output is caught in the socket

net/sixlowpan/sixlowpan_framelist.c

@@ -540,7 +540,7 @@ int sixlowpan_queue_frames(FAR struct radio_driver_s *radio,
       /* The outbound IPv6 packet is too large to fit into a single 15.4
        * packet, so we fragment it into multiple packets and send them.
        * The first fragment contains frag1 dispatch, then
-       * IPv6/HC1/HC06/HC_UDP dispatchs/headers.
+       * IPv6/HC1/HC06/HC_UDP dispatches/headers.
        * The following fragments contain only the fragn dispatch.
        */
 

net/sixlowpan/sixlowpan_input.c

@@ -718,7 +718,7 @@ static int sixlowpan_dispatch(FAR struct radio_driver_s *radio)
  *               radio, or (2) struct pktradio_metadata_s for a non-standard
  *               packet radio.
  *
- *               If there are multilple frames in the list, this metadata
+ *               If there are multiple frames in the list, this metadata
  *               must apply to all of the frames in the list.
  *
  * Returned Value:

net/sixlowpan/sixlowpan_reassbuf.c

@@ -134,7 +134,7 @@ static void sixlowpan_reass_expire(void)
       next = reass->rb_flink;
 
       /* Free any inactive reassembly buffers.  This is done because the life
-       * the reassembly buffer is not cerain.
+       * the reassembly buffer is not certain.
        */
 
       if (!reass->rb_active)

net/sixlowpan/sixlowpan_tcpsend.c

@@ -812,7 +812,7 @@ ssize_t psock_6lowpan_tcp_send(FAR struct socket *psock, FAR const void *buf,
  * Name: sixlowpan_tcp_send
  *
  * Description:
- *   TCP output comes through three different mechansims.  Either from:
+ *   TCP output comes through three different mechanisms.  Either from:
  *
  *   1. TCP socket output.  For the case of TCP output to an
  *      IEEE802.15.4, the TCP output is caught in the socket