openbmc-20160329-1

User application will poll OCC when host is powered off. OCC can handle
the poll request, but no sensor data will be responded. Currently OCC driver
will report error message when reading sysfs hwmon sensor attribute in this case.
The error message is harmless but is anoying.

This patch hides the error message. Reading sysfs hwmon attribute in this case
will still get an error code, but no more error message.

Signed-off-by: Yi Li <adamliyi@msn.com>
Signed-off-by: Joel Stanley <joel@jms.id.au>