power: reset: qcom-pon: reg write mask depends on pon generation

Instead of hardcode the mask, it should be depends
on which generation of pon it was.
Signed-off-by: Kejia Hu <kejia.hu@codethink.co.uk>
Fixes: fce5430f ("reset: qcom-pon: Add support for gen2 pon")
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/reset/qcom-pon.c

@@ -34,7 +34,8 @@ static int pm8916_reboot_mode_write(struct reboot_mode_driver *reboot,
 
 	ret = regmap_update_bits(pon->regmap,
 				 pon->baseaddr + PON_SOFT_RB_SPARE,
-				 0xfc, magic << pon->reason_shift);
+				 GENMASK(7, pon->reason_shift),
+				 magic << pon->reason_shift);
 	if (ret < 0)
 		dev_err(pon->dev, "update reboot mode bits failed\n");