In case of switching from non-optimized to optimized version
of BranchLong macro, we forgot to take the instruction which
is located in the branch delay slot of the unoptimized version
and copy it to branch delay slot of the optimized version.

This CL implements the missing functionality.

Change-Id: I5e4adcccd0e85fd381a97eea8588e07bd8b045ef
Reviewed-on: https://chromium-review.googlesource.com/1165082Reviewed-by: Ivica Bogosavljevic <ibogosavljevic@wavecomp.com>
Commit-Queue: Ivica Bogosavljevic <ibogosavljevic@wavecomp.com>
Cr-Commit-Position: refs/heads/master@{#54970}