[nrf fromtree] net: lib: coap_client: Const pointers in request

CoAP client does not modify any of the members, so
change all pointers to const.

Signed-off-by: Seppo Takalo <[email protected]>
(cherry picked from commit bc4f026)

Author: SeppoTakalo

include/zephyr/net/coap_client.h

@@ -53,16 +53,16 @@ typedef void (*coap_client_response_cb_t)(int16_t result_code,
  * @brief Representation of a CoAP client request.
  */
 struct coap_client_request {
-	enum coap_method method;            /**< Method of the request */
-	bool confirmable;	            /**< CoAP Confirmable/Non-confirmable message */
-	const char *path;	            /**< Path of the requested resource */
-	enum coap_content_format fmt;       /**< Content format to be used */
-	uint8_t *payload;	            /**< User allocated buffer for send request */
-	size_t len;		            /**< Length of the payload */
-	coap_client_response_cb_t cb;       /**< Callback when response received */
-	struct coap_client_option *options; /**< Extra options to be added to request */
-	uint8_t num_options;                /**< Number of extra options */
-	void *user_data;	            /**< User provided context */
+	enum coap_method method;                  /**< Method of the request */
+	bool confirmable;                         /**< CoAP Confirmable/Non-confirmable message */
+	const char *path;                         /**< Path of the requested resource */
+	enum coap_content_format fmt;             /**< Content format to be used */
+	const uint8_t *payload;                   /**< User allocated buffer for send request */
+	size_t len;                               /**< Length of the payload */
+	coap_client_response_cb_t cb;             /**< Callback when response received */
+	const struct coap_client_option *options; /**< Extra options to be added to request */
+	uint8_t num_options;                      /**< Number of extra options */
+	void *user_data;                          /**< User provided context */
 };
 
 /**