rtc: xilinx: Fix calibval variable type

This patch fixes the warnings reported by static code analysis.
Updated calibval variable type to unsigned type from signed.
Signed-off-by: Srinivas Goud <srinivas.goud@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Link: https://lore.kernel.org/r/20765c4c27aa92c75426b82fd2815ebef6471492.1570544738.git.michal.simek@xilinx.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-zynqmp.c

@@ -44,7 +44,7 @@ struct xlnx_rtc_dev {
 	void __iomem		*reg_base;
 	int			alarm_irq;
 	int			sec_irq;
-	int			calibval;
+	unsigned int		calibval;
 };
 
 static int xlnx_rtc_set_time(struct device *dev, struct rtc_time *tm)