rtc: nvmem: emit an error message when nvmem registration fails

Some users check the return value of devm_rtc_nvmem_register() only in
order to emit an error message and then continue probing. This is fine
as an rtc can function without exposing nvmem but let's generalize it:
let's make the registration function emit the error message so that
users don't have to.

Signed-off-by: Bartosz Golaszewski <[e-mail]>
Signed-off-by: Alexandre Belloni <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/rtc/nvmem.c

···
 int devm_rtc_nvmem_register(struct rtc_device *rtc,
 		       struct nvmem_config *nvmem_config)
 {
+	struct device *dev = rtc->dev.parent;
 	struct nvmem_device *nvmem;
 
 	if (!nvmem_config)
 		return -ENODEV;
 
-	nvmem_config->dev = rtc->dev.parent;
+	nvmem_config->dev = dev;
 	nvmem_config->owner = rtc->owner;
-	nvmem = devm_nvmem_register(rtc->dev.parent, nvmem_config);
+	nvmem = devm_nvmem_register(dev, nvmem_config);
+	if (IS_ERR(nvmem))
+		dev_err(dev, "failed to register nvmem device for RTC\n");
 
 	return PTR_ERR_OR_ZERO(nvmem);
 }

drivers/rtc/rtc-cmos.c

···
 
 	/* export at least the first block of NVRAM */
 	nvmem_cfg.size = address_space - NVRAM_OFFSET;
-	if (devm_rtc_nvmem_register(cmos_rtc.rtc, &nvmem_cfg))
-		dev_err(dev, "nvmem registration failed\n");
+	devm_rtc_nvmem_register(cmos_rtc.rtc, &nvmem_cfg);
 
 	dev_info(dev, "%s%s, %d bytes nvram%s\n",
 		 !is_valid_irq(rtc_irq) ? "no alarms" :

drivers/rtc/rtc-ds1553.c

···
 		}
 	}
 
-	if (devm_rtc_nvmem_register(pdata->rtc, &nvmem_cfg))
-		dev_err(&pdev->dev, "unable to register nvmem\n");
+	devm_rtc_nvmem_register(pdata->rtc, &nvmem_cfg);
 
 	return 0;
 }

drivers/rtc/rtc-ds1742.c

···
 	if (ret)
 		return ret;
 
-	if (devm_rtc_nvmem_register(rtc, &nvmem_cfg))
-		dev_err(&pdev->dev, "Unable to register nvmem\n");
+	devm_rtc_nvmem_register(rtc, &nvmem_cfg);
 
 	return 0;
 }