[Committed] Add -mno-stv to new gcc.target/i386/cmpti2.c test case.

Adding -march=cascadelake to the command line options of the new cmpti2.c
testcase triggers TImode STV and produces vector code that doesn't match
the scalar implementation that this test was intended to check.  Adding
-mno-stv to the options fixes this.  Committed as obvious.

2022-08-07  Roger Sayle  <roger@nextmovesoftware.com>

gcc/testsuite/ChangeLog
	* gcc.target/i386/cmpti2.c: Add -mno-stv to dg-options.

gcc/testsuite/gcc.target/i386/cmpti2.c

 /* { dg-do compile { target int128 } } */
-/* { dg-options "-O2" } */
+/* { dg-options "-O2 -mno-stv" } */
 
 __int128 x;
 __int128 y;