Revert "Check if an interrupt is latched for SRQ during every IRQ"

This reverts commit f7e1339b2cdc0b3ebe7a7ab0df4521256e772dd3.

Checking if an interrupt is latched for SRQ during every IRQ
worked on the P-series but causes the B-series to lock up.  With
it reverted, both machines work again.