[SCSI] ibmvscsi: Improve CRQ reset reliability

This patch fixes an issue seen where an event occurs
which causes the ibmvscsi driver to reset its CRQ. Upon
re-registering its CRQ, it receives H_CLOSED, indicating
the Virtual I/O Server is not yet ready to receive commands.
This resulted in the ibmvscsi driver essentially offlining
the adapter and not recovering. The fix is to re-enable
our interrupt so that when the Virtual I/O server is ready
and sends a CRQ init, we will be able to receive it and
resume initialization of the VSCSI adapter.

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