scsi: qla2xxx: fix fcport null pointer access.

This patch allocates DMA memory to prevent NULL pointer access for ct_sns
request while sending switch commands.

Signed-off-by: Quinn Tran <quinn.tran@cavium.com>
Signed-off-by: Himanshu Madhani <hmadhani@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>