pinctrl: pinctrl-at91-pio4: PM related attribute descriptions

Fixes the following W=1 kernel build warning(s):

 drivers/pinctrl/pinctrl-at91-pio4.c:132: warning: Function parameter or member 'pm_wakeup_sources' not described in 'atmel_pioctrl'
 drivers/pinctrl/pinctrl-at91-pio4.c:132: warning: Function parameter or member 'pm_suspend_backup' not described in 'atmel_pioctrl'
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Cc: Ludovic Desroches <ludovic.desroches@microchip.com>
Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200713144930.1034632-16-lee.jones@linaro.orgSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/pinctrl-at91-pio4.c

@@ -106,6 +106,8 @@ struct atmel_pin {
  * @irq_domain: irq domain for the gpio controller.
  * @irqs: table containing the hw irq number of the bank. The index of the
  *     table is the bank id.
+ * @pm_wakeup_sources: bitmap of wakeup sources (lines)
+ * @pm_suspend_backup: backup/restore register values on suspend/resume
  * @dev: device entry for the Atmel PIO controller.
  * @node: node of the Atmel PIO controller.
  */