RISC-V: Reorder insn cost match order to match corresponding expander match order

The corresponding expander (riscv-v.cc:expand_const_vector) matches
const_vec_duplicate_p before const_vec_series_p. Reorder to match this
behavior when calculating costs.

gcc/ChangeLog:

	* config/riscv/riscv.cc (riscv_const_insns): Relocate.

Signed-off-by: Patrick O'Neill <patrick@rivosinc.com>