[RISCV] Use canonical move instruction in RISCVAsmPrinter::EmitHwasanMemaccessSymbols.

We were using an OR with X0 which is the canonical move for AArch64.
The canonical move for RISC-V is ADDI reg1, reg2, 0.

Reviewed By: reames

Differential Revision: https://reviews.llvm.org/D142044