[RISCV][ISel] Allow opaque constants in `hasAndNotCompare` (#92926)

See the following code:

https://github.com/llvm/llvm-project/blob/4ae896fe979b7db501cabde4b6b3504478958682/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp#L9334-L9357

> Combining: t47: i64 = xor t43, OpaqueConstant:i64<31808>
X: i64 = Constant<0>
Y: i64 = OpaqueConstant<31808>

The assertion failed because both `X` and `Y` are constants.
This patch allows opaque constants in `hasAndNotCompare` to fix the
issue.

Fixes https://github.com/llvm/llvm-project/issues/90730.