qla2xxx: Disable PCI device in shutdown handler.

Disable the PCI device during shutdown to prevent any races with
other PCI code such as the AER handling code.

Signed-off-by: Chad Dupuis <chad.dupuis@qlogic.com>
Signed-off-by: Saurav Kashyap <saurav.kashyap@qlogic.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>