[SCSI] ibmvfc: Log link up/down events

By default, ibmvfc does not log any async events in order
to avoid flooding the log with them. Improve on this by
logging by default events that are not likely to flood the
log, such as link up/down. Having these events in the log
will improve the ability to debug issues with ibmvfc.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>