[SCSI] ibmvfc: Handle Virtual I/O Server reboot

If a Virtual I/O server is rebooted, the client fibre channel sees a
transport event on its CRQ, which causes it to attempt to reconnect
to the CRQ. For a period of time during the VIOS reboot, the client's
attempts to register the CRQ will return H_CLOSED, indicating the server
side is not currently registered. The ibmvfc driver was not handling
this well and was taking the virtual adapter offline. Fix this by
re-enabling our interrupt and waiting for the event on our CRQ
indicating the server is back, at which point we can reconnect.

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