[RISCV][LegalizeTypes] Try to expand BSWAP before promoting if the promoted...

[RISCV][LegalizeTypes] Try to expand BSWAP before promoting if the promoted BSWAP would expand anyway.

If we're going to end up expanding anyway, we should do it early
so we don't create extra operations to handle the bytes added by
promotion.

This is helfpul on RISCV where we might have to promote i16 all
the way to i64.

Differential Revision: https://reviews.llvm.org/D95756