scsi: vmw_pscsi: Rearrange code to avoid multiple calls to free_irq during unload

Currently pvscsi_remove calls free_irq more than once as
pvscsi_release_resources and __pvscsi_shutdown both call
pvscsi_shutdown_intr. This results in a 'Trying to free already-free IRQ'
warning and stack trace. To solve the problem pvscsi_shutdown_intr has been
moved out of pvscsi_release_resources.

Signed-off-by: Cathy Avery <cavery@redhat.com>
Reviewed-by: Ewan D. Milne <emilne@redhat.com>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>