watchdog: pm8916_wdt: Avoid read of write-only PET register

PMIC_WD_RESET_PET is a write-only register that is used to ping
the watchdog. It does not make sense to use read-modify-write
for it: a register read will never return anything but zero.
(And actually even if it did we would still want to write again
to ensure the watchdog is pinged.)

Reduce the overhead for the watchdog ping slightly by using
regmap_write() directly instead.
Signed-off-by: Stephan Gerhold <stephan.gerhold@kernkonzept.com>
Reviewed-by: Loic Poulain <loic.poulain@linaro.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20220629084816.125515-2-stephan.gerhold@kernkonzept.comSigned-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

drivers/watchdog/pm8916_wdt.c

@@ -58,9 +58,8 @@ static int pm8916_wdt_ping(struct watchdog_device *wdev)
 {
 	struct pm8916_wdt *wdt = watchdog_get_drvdata(wdev);
 
-	return regmap_update_bits(wdt->regmap,
-				  wdt->baseaddr + PON_PMIC_WD_RESET_PET,
-				  WATCHDOG_PET_BIT, WATCHDOG_PET_BIT);
+	return regmap_write(wdt->regmap, wdt->baseaddr + PON_PMIC_WD_RESET_PET,
+			    WATCHDOG_PET_BIT);
 }
 
 static int pm8916_wdt_configure_timers(struct watchdog_device *wdev)