rtc: em3027: correct month value

The RTC month value is 1-indexed, but the kernel assumes it is 0-indexed.
This may result in the RTC not rolling over correctly.
Signed-off-by: Ilya Ledvich <ilya@compulab.co.il>
Reviewed-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
Link: https://lore.kernel.org/r/20191101095422.14787-1-ilya@compulab.co.ilSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-em3027.c

@@ -71,7 +71,7 @@ static int em3027_get_time(struct device *dev, struct rtc_time *tm)
 	tm->tm_hour	= bcd2bin(buf[2]);
 	tm->tm_mday	= bcd2bin(buf[3]);
 	tm->tm_wday	= bcd2bin(buf[4]);
-	tm->tm_mon	= bcd2bin(buf[5]);
+	tm->tm_mon	= bcd2bin(buf[5]) - 1;
 	tm->tm_year	= bcd2bin(buf[6]) + 100;
 
 	return 0;
@@ -94,7 +94,7 @@ static int em3027_set_time(struct device *dev, struct rtc_time *tm)
 	buf[3] = bin2bcd(tm->tm_hour);
 	buf[4] = bin2bcd(tm->tm_mday);
 	buf[5] = bin2bcd(tm->tm_wday);
-	buf[6] = bin2bcd(tm->tm_mon);
+	buf[6] = bin2bcd(tm->tm_mon + 1);
 	buf[7] = bin2bcd(tm->tm_year % 100);
 
 	/* write time/date registers */