rtc: m41t80: Correct alarm month range with RTC reads

commit 3cc9ffb upstream.

Add the missing adjustment of the month range on alarm reads from the
RTC, correcting an issue coming from commit 9c6dfed ("rtc: m41t80:
add alarm functionality").  The range is 1-12 for hardware and 0-11 for
`struct rtc_time', and is already correctly handled on alarm writes to
the RTC.

It was correct up until commit 48e9766 ("drivers/rtc/rtc-m41t80.c:
remove disabled alarm functionality") too, which removed the previous
implementation of alarm support.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Fixes: 9c6dfed ("rtc: m41t80: add alarm functionality")
References: 48e9766 ("drivers/rtc/rtc-m41t80.c: remove disabled alarm functionality")
Cc: stable@vger.kernel.org # 4.7+
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/rtc/rtc-m41t80.c

@@ -333,7 +333,7 @@ static int m41t80_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 	alrm->time.tm_min  = bcd2bin(alarmvals[3] & 0x7f);
 	alrm->time.tm_hour = bcd2bin(alarmvals[2] & 0x3f);
 	alrm->time.tm_mday = bcd2bin(alarmvals[1] & 0x3f);
-	alrm->time.tm_mon  = bcd2bin(alarmvals[0] & 0x3f);
+	alrm->time.tm_mon  = bcd2bin(alarmvals[0] & 0x3f) - 1;
 
 	alrm->enabled = !!(alarmvals[0] & M41T80_ALMON_AFE);
 	alrm->pending = (flags & M41T80_FLAGS_AF) && alrm->enabled;