testsuite: fix the condition bug in tsvc s176

This patch fixes the problem that the loop in the tsvc s176 function is
optimized and removed because `iterations/LEN_1D` is 0 (where iterations
is set to 10000, LEN_1D is set to 32000 in tsvc.h).

This testcase passed on x86 and AArch64 system.

Best,
Lehua

gcc/testsuite/ChangeLog:

	* gcc.dg/vect/tsvc/vect-tsvc-s176.c: Adjust iterations.
	* gcc.dg/vect/tsvc/tsvc.h: Adjust expected rsult for s176.