watchdog: sp805: Fix kernel doc description

Kernel doc validation script is not happy

  CHECK   .../sp805_wdt.c
  .../sp805_wdt.c:73: warning: Function parameter or member 'rate' not described in 'sp805_wdt'

Fix this by describing rate parameter.

While at it, mark clk one optional.

Fixes: dc0e4a3bb7 ("watchdog: sp805: Add clock-frequency property")
Cc: Srinath Mannam <srinath.mannam@broadcom.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20210517174912.26419-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

drivers/watchdog/sp805_wdt.c

@@ -57,7 +57,8 @@
  * @wdd: instance of struct watchdog_device
  * @lock: spin lock protecting dev structure and io access
  * @base: base address of wdt
- * @clk: clock structure of wdt
+ * @clk: (optional) clock structure of wdt
+ * @rate: (optional) clock rate when provided via properties
  * @adev: amba device structure of wdt
  * @status: current status of wdt
  * @load_val: load value to be set for current timeout