[RISCV] Use default promotion for (i32 (shl 1, X)) on RV64 when Zbs is enabled.

[RISCV] Use default promotion for (i32 (shl 1, X)) on RV64 when Zbs is enabled.

This improves opportunities to use bset/bclr/binv. Unfortunately,
there are no W versions of these instrcutions so this isn't always
a clear win. If we use SLLW we get free sign extend and shift masking,
but need to put a 1 in a register and can't remove an or/xor. If
we use bset/bclr/binv we remove the immediate materializationg and
logic op, but might need a mask on the shift amount and sext.w.

Reviewed By: luismarques

Differential Revision: https://reviews.llvm.org/D124096