This is a follow up from 39bf765bb671fa7df3fe6c164cc9532fcb8653bd,
for the other case handled here. We would create CopyToReg marked
as uniform, even though the end phi would need to use VGPRs due
to another divergent input. There's no directly observable change in
the final output of the new test, but it does hit this case.
ecec7d15a7