rtc: bq4802: add error handling for devm_ioremap

When devm_ioremap fails, the lack of error-handling code may
cause unexpected results.

This patch adds error-handling code after calling devm_ioremap.
Signed-off-by: NZhouyang Jia <jiazhouyang09@gmail.com>
Signed-off-by: NAlexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-bq4802.c

@@ -162,6 +162,10 @@ static int bq4802_probe(struct platform_device *pdev)
 	} else if (p->r->flags & IORESOURCE_MEM) {
 		p->regs = devm_ioremap(&pdev->dev, p->r->start,
 					resource_size(p->r));
+		if (!p->regs){
+			err = -ENOMEM;
+			goto out;
+		}
 		p->read = bq4802_read_mem;
 		p->write = bq4802_write_mem;
 	} else {