aarch64: Add option to pr105219 testcase

Add option that originally caused testcase to fail for aarch64.

gcc/testsuite/ChangeLog:

	PR tree-optimization/105219
	* gcc.dg/vect/pr105219.c: Add aarch64 target option.

gcc/testsuite/gcc.dg/vect/pr105219.c

 /* { dg-do run } */
 /* { dg-additional-options "-O3" } */
 /* { dg-additional-options "-mtune=intel" { target x86_64-*-* i?86-*-* } } */
+/* { dg-additional-options "-mtune=thunderx" { target aarch64*-*-* } } */
 
 #include "tree-vect.h"