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: cd5676db ("misc: eeprom: at24: support pm_runtime control")
Fixes: b20eb4c1 ("eeprom: at24: drop unnecessary label")
Cc: stable@vger.kernel.org
Signed-off-by: Vadym Kochan <vadym.kochan@plvision.eu>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

drivers/misc/eeprom/at24.c

@@ -692,10 +692,6 @@ static int at24_probe(struct i2c_client *client)
 	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);
@@ -708,6 +704,13 @@ static int at24_probe(struct i2c_client *client)
 	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
 	 * chip is functional.