scsi: csiostor: create per port irq affinity mask set

csiostor driver allocates per port num_online_cpus() irq vectors, so create
per-port irq affinity mask set to spread irq vectors evenly.

Signed-off-by: Varun Prakash <varun@chelsio.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>