All that really matters is that the VLMAX of the preceding
instructions is the same as the VLMAX required by the mask
operation.
Also update the vmsge(u) handling to use the SEW/LMUL we use for
other mask register operations. We were matching it to the compare
before. Some cases will be improve if we fix masked compares to
use tail agnostic policy. I think they ignore the tail policy
anyway.
I'm finding this comment a little confusing in that it says "unless this is a mask reg operation" but only (explicitly) checks Other.MaskRegOp. Is "this" implied, or should the comment be updated?