rtc: m41t80: Correct alarm month range with RTC reads

commit 3cc9ffbb1f51eb4320575a48e4805a8f52e0e26b upstream.

Add the missing adjustment of the month range on alarm reads from the
RTC, correcting an issue coming from commit 9c6dfed92c3e ("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 48e9766726eb ("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: 9c6dfed92c3e ("rtc: m41t80: add alarm functionality")
References: 48e9766726eb ("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

@@ -393,7 +393,7 @@ 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;