RISC-V: Remove duplicate `order_operator' predicate

RISC-V: Remove duplicate `order_operator' predicate

Remove our RISC-V-specific `order_operator' predicate, which is exactly
the same as generic `ordered_comparison_operator' one.

	gcc/
	* config/riscv/predicates.md (order_operator): Remove predicate.
	* config/riscv/riscv.cc (riscv_rtx_costs): Update accordingly.
	* config/riscv/riscv.md (*branch<mode>, *mov<GPR:mode><X:mode>cc)
	(cstore<mode>4): Likewise.