[RISCV][ISel] Eliminate `andi rd, rs1, -1` instructions (#89976)

Inspired by https://github.com/llvm/llvm-project/pull/89966, this patch
handles the special case `binop_allwusers<and> GPR:$rs1, 0xffffffff ->
copy $rs1` to avoid creating redundant `andi rd, rs1, -1` instructions.