Fix PR testsuite/116271, gcc.dg/vect/tsvc/vect-tsvc-s176.c fails

gcc/testsuite:
	PR testsuite/116271
	* gcc.dg/vect/tsvc/vect-tsvc-s176.c [TRUNCATE_TEST]: Make sure
	that m stays the same as the loop bound of the middle loop.
	* gcc.dg/vect/tsvc/tsvc.h (get_expected_result) <s176> [TRUNCATE_TEST]:
	Adjust expected value.