watchdog: docs: kernel-api: don't reference removed functions

Those functions are not only deprecated, but gone for good.

Fixes: 62cd1c40 ("watchdog: kill unref/ref ops")
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

Documentation/watchdog/watchdog-kernel-api.txt

@@ -128,8 +128,6 @@ struct watchdog_ops {
 	int (*set_pretimeout)(struct watchdog_device *, unsigned int);
 	unsigned int (*get_timeleft)(struct watchdog_device *);
 	int (*restart)(struct watchdog_device *);
-	void (*ref)(struct watchdog_device *) __deprecated;
-	void (*unref)(struct watchdog_device *) __deprecated;
 	long (*ioctl)(struct watchdog_device *, unsigned int, unsigned long);
 };
 
@@ -218,8 +216,6 @@ they are supported. These optional routines/operations are:
   if a command is not supported. The parameters that are passed to the ioctl
   call are: watchdog_device, cmd and arg.
 
-The 'ref' and 'unref' operations are no longer used and deprecated.
-
 The status bits should (preferably) be set with the set_bit and clear_bit alike
 bit-operations. The status bits that are defined are:
 * WDOG_ACTIVE: this status bit indicates whether or not a watchdog timer device