hwmon: (ibmaem) Fix return value

Propagate appropriate error code obtained from ipmi_create_user()
instead of hardcoding.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Acked-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>