RISC-V: Update Xsfvqmacc and Xsfvfnrclip's testcases

Update Sifive Xsfvqmacc and Xsfvfnrclip extension's testcases.

version log:
	Update synchronize LMUL settings with return type.

gcc/ChangeLog:

	* config/riscv/vector.md: New attr set.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/xsfvector/sf_vfnrclip_x_f_qf.c: Add vsetivli checking.
	* gcc.target/riscv/rvv/xsfvector/sf_vfnrclip_xu_f_qf.c: Ditto.
	* gcc.target/riscv/rvv/xsfvector/sf_vqmacc_2x8x2.c: Ditto.
	* gcc.target/riscv/rvv/xsfvector/sf_vqmacc_4x8x4.c: Ditto.
	* gcc.target/riscv/rvv/xsfvector/sf_vqmaccsu_2x8x2.c: Ditto.
	* gcc.target/riscv/rvv/xsfvector/sf_vqmaccsu_4x8x4.c: Ditto.
	* gcc.target/riscv/rvv/xsfvector/sf_vqmaccu_2x8x2.c: Ditto.
	* gcc.target/riscv/rvv/xsfvector/sf_vqmaccu_4x8x4.c: Ditto.
	* gcc.target/riscv/rvv/xsfvector/sf_vqmaccus_2x8x2.c: Ditto.
	* gcc.target/riscv/rvv/xsfvector/sf_vqmaccus_4x8x4.c: Ditto.