scsi: qla2xxx: Check for Register disconnect

[ Upstream commit f99c5d294b3653e6ae563eaac5db5b4138afe31c ]

During adapter shutdown process check for register disconnect before
proceeding to call PCI functions.

Signed-off-by: Sawan Chandak <sawan.chandak@cavium.com>
Signed-off-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>