[SCSI] qla2xxx: Correct inadvertent clearing of RISC_INTR status.

During heavy I/O (CPU-affinity mode enabled) and CLI/Agent
interactions, the driver would report periodic mailbox command
timeout statuses.  Within the CPU-affinity ISR handler, the
driver should check the 'disable-msix-handshake' flag in deciding
whether or not to clear HCCRX_CLR_RISC_INT.  The mode is not
specific to a dedicated queue, instead, applies to the current
'ha' context.

Signed-off-by: Andrew Vasquez <andrew.vasquez@qlogic.com>
Signed-off-by: Chad Dupuis <chad.dupuis@qlogic.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>