[RISCV] Check whether plain type is supported for permutation intrinsics instead of its float type (#146657)
For permutation intrinsics, the float data type is not used during
processing. We only need to check whether its plain type is supported,
rather than the float type. This is like what we did in
https://github.com/llvm/llvm-project/blob/651c5208f8597f1f80349f6208e69bf9ea1c2862/llvm/lib/Target/RISCV/RISCVInstrInfoVVLPatterns.td#L2958