[committed][RISC-V]Don't reject constants in cmov condition

[committed][RISC-V]Don't reject constants in cmov condition

This test is too aggressive.  Constants have VOIDmode, so we need to let the
through this phase of conditional move support.

Fixes several missed conditional moves with the trunk.

gcc/
	* config/riscv/riscv.cc (riscv_expand_conditional_move): Allow
	VOIDmode operands to conditional before canonicalization.