scsi: qla2xxx: Use a dedicated interrupt handler for 'handshake-required' ISPs

There's no point checking flags.disable_msix_handshake in the
interrupt handler hot-path.  Instead perform the check during
queue-pair instantiation and use the proper interrupt handler.

Link: https://lore.kernel.org/r/20200226224022.24518-8-hmadhani@marvell.com


Signed-off-by: Himanshu Madhani <hmadhani@marvell.com>
Signed-off-by: Andrew Vasquez <andrewv@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>