[RISCV] Optimize multiplication with constant

1. Break MUL with specific constant to a SLLI and an ADD/SUB on riscv32
   with the M extension.
2. Break MUL with specific constant to two SLLI and an ADD/SUB, if the
   constant needs a pair of LUI/ADDI to construct.

Reviewed by: craig.topper

Differential Revision: https://reviews.llvm.org/D93619