[SCSI] qla4xxx: Fix double clearing of risc_intr for ISP83XX

Issue:
For ISP83XX risc_intr getting clear two times in case of polling mode.
risc_intr getting clear from interrupt_service_routine() as well
from process_mbox_intr() because of this driver may clear risc_intr
without processing interrupt.

Fix:
Do not clear risc_intr from process_mbox_intr().
Signed-off-by: Manish Dusane <manish.dusane@qlogic.com>
Signed-off-by: Vikas Chaudhary <vikas.chaudhary@qlogic.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

drivers/scsi/qla4xxx/ql4_83xx.c

@@ -1402,7 +1402,6 @@ void qla4_83xx_process_mbox_intr(struct scsi_qla_host *ha, int outcount)
 		ha->mbox_status_count = outcount;
 		ha->isp_ops->interrupt_service_routine(ha, intr_status);
 	}
-	writel(0, &ha->qla4_83xx_reg->risc_intr);
 }
 
 /**