hwmon: (ibmaem) Make instance initializations independent

There is no good reason that I can see why the failure to initialize
one instance should prevent other instances from being initialized.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Darrick J. Wong <djwong@us.ibm.com>
Acked-by: Guenter Roeck <guenter.roeck@ericsson.com>