hwmon: (pmbus/adm1266) register the nvmem device after pmbus_do_probe()

adm1266_probe() calls adm1266_config_nvmem() -- which goes on to
devm_nvmem_register() and exposes adm1266_nvmem_read() to userspace --
before pmbus_do_probe() has initialised the per-client PMBus state.

Same latent hazard as the gpio_chip one fixed in the previous patch:
once the nvmem device is registered, gpiolib's nvmem char-dev / sysfs
interface is reachable, and any concurrent read triggers
adm1266_nvmem_read() -> adm1266_nvmem_read_blackbox(), which issues
PMBus traffic that races pmbus_do_probe()'s own device accesses with
no serialisation.

Move adm1266_config_nvmem() down past pmbus_do_probe() so the nvmem
device isn't reachable from userspace until the PMBus state the
nvmem accessors depend on is fully initialised.

Fixes: 15609d1 ("hwmon: (pmbus/adm1266) read blackbox")
Cc: stable@vger.kernel.org
Signed-off-by: Abdurrahman Hussain <abdurrahman@nexthop.ai>
Link: https://lore.kernel.org/r/20260518-adm1266-gpio-fixes-v3-5-e425e4f88139@nexthop.ai
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Author: abdurrahman-nexthop

drivers/hwmon/pmbus/adm1266.c

@@ -477,14 +477,14 @@ static int adm1266_probe(struct i2c_client *client)
 	if (ret < 0)
 		return ret;
 
-	ret = adm1266_config_nvmem(data);
-	if (ret < 0)
-		return ret;
-
 	ret = pmbus_do_probe(client, &data->info);
 	if (ret)
 		return ret;
 
+	ret = adm1266_config_nvmem(data);
+	if (ret < 0)
+		return ret;
+
 	ret = adm1266_config_gpio(data);
 	if (ret < 0)
 		return ret;