Increased KLxxZs interrupt handling speed

Instead of checking one bit at a time use a simple binary search
algorithm. Speed increase is roughly 150% (bit more for KL46).

(Got a bit too optimistic in commit message, speed is 250% compared to original speed, so increase 150%. Original could handle roughly 90k interrupts per second (70k KL46), this one continues working until 240k (230k for KL46))