Add new attribute "vpm" to the subchannel sysfs directory of I/O
subchannels. This attribute contains a path mask indicating which
channel paths were successfully verified to be usable for I/O.
Reviewed-by: NPeter Oberparleiter <peter.oberparleiter@de.ibm.com>
Signed-off-by: NSebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>