Per channel path measurement characteristics are obtained during channel
path registration. However if some properties of a channel path change
we don't update the measurement characteristics.

Make sure to update the characteristics when we change the properties of
a channel path or receive a notification from FW about such a change.
Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>