nvme-hwmon: consistently ignore errors from nvme_hwmon_init

An NVMe controller works perfectly fine even when the hwmon
initialization fails.  Stop returning errors that do not come from a
controller reset from nvme_hwmon_init to handle this case consistently.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Serge Semin <fancer.lancer@gmail.com>