[JumpThreading] Don't limit the type of an operand

Compared to the optimized code with branch conditions never frozen,
limiting the type of freeze's operand causes generation of suboptimal code in
some cases.
I would like to suggest removing the constraint, as this patch does.
If the number of freeze instructions becomes significant, this can be revisited.

Differential Revision: https://reviews.llvm.org/D84949