RISC-V: Update Xsfvfnrclip implementation.

Update implementation of Xsfvfnrclip, using return type as iterator.

gcc/ChangeLog:

	* config/riscv/genrvv-type-indexer.cc (expand_floattype): New func.
	(main): New type.
	* config/riscv/riscv-vector-builtins-types.def (DEF_RVV_XFQF_OPS): New def.
	(vint8mf8_t): Ditto.
	(vint8mf4_t): Ditto.
	(vint8mf2_t): Ditto.
	(vint8m1_t): Ditto.
	(vint8m2_t): Ditto.
	* config/riscv/riscv-vector-builtins.cc (DEF_RVV_XFQF_OPS): Ditto.
	(rvv_arg_type_info::get_xfqf_float_type): Ditto.
	* config/riscv/riscv-vector-builtins.def (xfqf_vector): Ditto.
	(xfqf_float): Ditto.
	* config/riscv/riscv-vector-builtins.h
	(struct rvv_arg_type_info): New function prototype.
	* config/riscv/sifive-vector.md: Update iterator.
	* config/riscv/vector-iterators.md: Ditto.