rtc: nvmem: don't use IS_ERR_OR_NULL

nvmem_register() never returns NULL, so IS_ERR is good enough here.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/nvmem.c

@@ -94,7 +94,7 @@ int rtc_nvmem_register(struct rtc_device *rtc,
 	nvmem_config->dev = rtc->dev.parent;
 	nvmem_config->owner = rtc->owner;
 	rtc->nvmem = nvmem_register(nvmem_config);
-	if (IS_ERR_OR_NULL(rtc->nvmem))
+	if (IS_ERR(rtc->nvmem))
 		return PTR_ERR(rtc->nvmem);
 
 	/* Register the old ABI */