rtc: rzn1: Fix a variable type

The calculation in ->set_offset() handles both negative and positive
offsets. The 'steps' variable will be checked to be in a specific [-x;
+x] range, which means it must be a signed integer rather than
unsigned.

This also fixes the following smatch warning:

     warn: 'steps' 'true' implies 'steps > 0' is 'true'

Fixes: be4a11cf98 ("rtc: rzn1: Add oscillator offset support")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20220520082500.489248-1-miquel.raynal@bootlin.com

drivers/rtc/rtc-rzn1.c

@@ -270,8 +270,7 @@ static int rzn1_rtc_read_offset(struct device *dev, long *offset)
 static int rzn1_rtc_set_offset(struct device *dev, long offset)
 {
 	struct rzn1_rtc *rtc = dev_get_drvdata(dev);
-	unsigned int steps;
-	int stepsh, stepsl;
+	int stepsh, stepsl, steps;
 	u32 subu = 0, ctl2;
 	int ret;