[docs] fix typos in comments (#3417)

include/openthread/coap_secure.h

@@ -247,7 +247,7 @@ bool otCoapSecureIsConncetionActive(otInstance *aInstance);
  *
  * @retval OT_ERROR_NONE           Successfully sent CoAP message.
  * @retval OT_ERROR_NO_BUFS        Failed to allocate retransmission data.
- * @retvak OT_ERROR_INVALID_STATE  DTLS connection was not initialized.
+ * @retval OT_ERROR_INVALID_STATE  DTLS connection was not initialized.
  *
  */
 otError otCoapSecureSendRequest(otInstance *          aInstance,

include/openthread/message.h

@@ -89,7 +89,7 @@ typedef struct otBufferInfo
 } otBufferInfo;
 
 /**
- * This enumeration defines the Openthread message priority levels.
+ * This enumeration defines the OpenThread message priority levels.
  *
  */
 typedef enum otMessagePriority

include/openthread/network_time.h

@@ -53,7 +53,7 @@ extern "C" {
  */
 
 /**
- * This enum represents OpenThread time synchronization status.
+ * This enumeration represents OpenThread time synchronization status.
  *
  */
 typedef enum otNetworkTimeStatus

include/openthread/udp.h

@@ -237,7 +237,7 @@ typedef void (*otUdpForwarder)(otMessage *   aMessage,
                                void *        aContext);
 
 /**
- * Set UDP forward callback to deliever UDP packets to host.
+ * Set UDP forward callback to deliver UDP packets to host.
  *
  * @param[in]  aInstance            A pointer to an OpenThread instance.
  * @param[in]  aForwarder           A pointer to a function called to forward UDP packet to host.