watchdog: clarify that stop() is optional

The commit d0684c8a ("watchdog: Make stop function optional")
made stop function not mandatory, but the comments
and the doc weren't reflected. Fix it to clarify.
Signed-off-by: Bumsik Kim <k.bumsik@gmail.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20200403031507.63487-1-k.bumsik@gmail.comSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/watchdog/convert_drivers_to_kernel_api.rst

@@ -115,7 +115,7 @@ Add the watchdog operations
 ---------------------------
 
 All possible callbacks are defined in 'struct watchdog_ops'. You can find it
-explained in 'watchdog-kernel-api.txt' in this directory. start(), stop() and
+explained in 'watchdog-kernel-api.txt' in this directory. start() and
 owner must be set, the rest are optional. You will easily find corresponding
 functions in the old driver. Note that you will now get a pointer to the
 watchdog_device as a parameter to these functions, so you probably have to

Documentation/watchdog/watchdog-kernel-api.rst

@@ -123,8 +123,8 @@ The list of watchdog operations is defined as::
 	struct module *owner;
 	/* mandatory operations */
 	int (*start)(struct watchdog_device *);
-	int (*stop)(struct watchdog_device *);
 	/* optional operations */
+	int (*stop)(struct watchdog_device *);
 	int (*ping)(struct watchdog_device *);
 	unsigned int (*status)(struct watchdog_device *);
 	int (*set_timeout)(struct watchdog_device *, unsigned int);

include/linux/watchdog.h

@@ -37,15 +37,15 @@ struct watchdog_governor;
  *
  * The watchdog_ops structure contains a list of low-level operations
  * that control a watchdog device. It also contains the module that owns
- * these operations. The start and stop function are mandatory, all other
+ * these operations. The start function is mandatory, all other
  * functions are optional.
  */
 struct watchdog_ops {
 	struct module *owner;
 	/* mandatory operations */
 	int (*start)(struct watchdog_device *);
-	int (*stop)(struct watchdog_device *);
 	/* optional operations */
+	int (*stop)(struct watchdog_device *);
 	int (*ping)(struct watchdog_device *);
 	unsigned int (*status)(struct watchdog_device *);
 	int (*set_timeout)(struct watchdog_device *, unsigned int);