[RISCV] Remove redundant vand.vi with fpto*i to i1 (#179876)
If the source of an fpto*i doesn't fit in the destination type, the
result is poison. For i1 destinations, this means the result needs to be
0 or 1/-1, so we can just compare the result to 0 directly instead of
truncating.
The VP lowering for fpto*i already does this.