scsi: qla2xxx: Change in PUREX to handle FPIN ELS requests

SAN Congestion Management generates ELS pkts whose size can vary and be >
64 bytes. Change the PUREX handling code to support non-standard ELS pkt
size.

Link: https://lore.kernel.org/r/20200630102229.29660-2-njavali@marvell.com


Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Shyam Sundar <ssundar@marvell.com>
Signed-off-by: Arun Easi <aeasi@marvell.com>
Signed-off-by: Nilesh Javali <njavali@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>