s390/dasd: Fix operational path inconsistency

During online processing and setting up a DASD device, the configuration
data for operational paths is read and validated two times
(dasd_eckd_read_conf()). The first time to provide information that are
necessary for the LCU setup. A second time after the LCU setup as a
device might report different configuration data then.

When the configuration setup for each operational path is being
validated, an initial call to dasd_eckd_clear_conf_data() is issued.
This call wipes all previously available configuration data and path
information for each path.
However, the operational path mask is not updated during this process.

As a result, the stored operational path mask might no longer correspond
to the operational paths mask reported by the CIO layer, as several
paths might be gone between the two dasd_eckd_read_conf() calls.

This inconsistency leads to more severe issues in later path handling
changes. Fix this by removing the channel paths from the operational
path mask during the dasd_eckd_clear_conf_data() call.

Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Reviewed-by: Stefan Haberland <sth@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>