[Bug target/80482] [7/8 Regression] vec_mul produces compilation error if 1 of its parms is const or volatile

[seurer at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80482

--- Comment #3 from seurer at gcc dot gnu.org ---
Yeah, I was going to try something like that.  There are some other places this
probably need to be done too.