RISC-V: Refine the testcase of vector SAT_SUB

Take scan-assembler-times for vssub insn check instead of function body,
as we only care about if we can generate the fixed point insn vssub.

The below test are passed for this patch.
* The rv64gcv fully regression test.

It is test only patch and obvious up to a point, will commit it
directly if no comments in next 48H.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-1.c: Remove
	func body check and take scan asm times instead.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-10.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-11.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-12.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-13.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-14.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-15.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-16.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-17.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-18.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-19.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-2.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-20.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-21.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-22.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-23.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-24.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-25.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-26.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-27.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-28.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-29.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-3.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-30.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-31.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-32.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-33.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-34.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-35.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-36.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-37.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-38.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-39.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-4.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-40.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-5.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-6.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-7.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-8.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub-9.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub_trunc-1.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub_trunc-2.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub_trunc-3.c: Ditto.
	* gcc.target/riscv/rvv/autovec/binop/vec_sat_u_sub_zip.c: Ditto.

Signed-off-by: Pan Li <pan2.li@intel.com>