execute1: Add latch to redirect path

execute1: Add latch to redirect path

This latches the redirect signal inside execute1, so that it is sent
a cycle later to fetch1 (and to decode/icache as flush).  This breaks
a long combinatorial chain from the branch and interrupt detection
in execute1 through the redirect/flush signals all the way back to
fetch1, icache and decode.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>