misc: eeprom: at24: register nvmem only after eeprom is ready to use

During nvmem_register() the nvmem core sends notifications when:

- cell added
- nvmem added

and during these notifications some callback func may access the nvmem
device, which will fail in case of at24 eeprom because regulator and pm
are enabled after nvmem_register().

Fixes: cd5676db0574 ("misc: eeprom: at24: support pm_runtime control")
Fixes: b20eb4c1f026 ("eeprom: at24: drop unnecessary label")
Cc: [e-mail]
Signed-off-by: Vadym Kochan <[e-mail]>
Signed-off-by: Bartosz Golaszewski <[e-mail]>

drivers/misc/eeprom/at24.c

···
 	nvmem_config.word_size = 1;
 	nvmem_config.size = byte_len;
 
-	at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
-	if (IS_ERR(at24->nvmem))
-		return PTR_ERR(at24->nvmem);
-
 	i2c_set_clientdata(client, at24);
 
 	err = regulator_enable(at24->vcc_reg);
···
 	/* enable runtime pm */
 	pm_runtime_set_active(dev);
 	pm_runtime_enable(dev);
+
+	at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
+	if (IS_ERR(at24->nvmem)) {
+		pm_runtime_disable(dev);
+		regulator_disable(at24->vcc_reg);
+		return PTR_ERR(at24->nvmem);
+	}
 
 	/*
 	 * Perform a one-byte test read to verify that the