RISC-V: Simplify EQ vs NE selection in `riscv_expand_conditional_move'

Just choose between EQ and NE at `gen_rtx_fmt_ee' invocation, removing
an extraneous variable only referred once and improving code clarity.

	gcc/
	* config/riscv/riscv.cc (riscv_expand_conditional_move): Remove
	extraneous variable for EQ vs NE operation selection.