rtc: rv8803: fix writing back ctrl in flag register

ctrl is set from read_regs(..FLAG, 2, ctrl), so ctrl[0] is FLAG
and ctrl[1] is the CTRL register.
Use ctrl[0] to write back to the FLAG register as appropriate.

Signed-off-by: Dominique Martinet <dominique.martinet@atmark-techno.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20211101013400.325855-1-dominique.martinet@atmark-techno.com
diff --git a/drivers/rtc/rtc-rv8803.c b/drivers/rtc/rtc-rv8803.c
index 72adef5..0d5ed38 100644
--- a/drivers/rtc/rtc-rv8803.c
+++ b/drivers/rtc/rtc-rv8803.c
@@ -340,8 +340,8 @@ static int rv8803_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 		}
 	}
 
-	ctrl[1] &= ~RV8803_FLAG_AF;
-	err = rv8803_write_reg(rv8803->client, RV8803_FLAG, ctrl[1]);
+	ctrl[0] &= ~RV8803_FLAG_AF;
+	err = rv8803_write_reg(rv8803->client, RV8803_FLAG, ctrl[0]);
 	mutex_unlock(&rv8803->flags_lock);
 	if (err)
 		return err;