testsuite: XFAIL test in pr109393.c for ilp32 targets [PR116845]

The match.pd canonicalization that this testcase checks for,
is not applied on ilp32 targets.

This XFAILs the test on ilp32 targets.

	PR testsuite/116845

gcc/testsuite/ChangeLog:

	* gcc.dg/pr109393.c: XFAIL on ilp32 targets.

gcc/testsuite/gcc.dg/pr109393.c

@@ -20,4 +20,5 @@ int bar(int *a, int j)
   return (&a[j + 1] - 2) == &a[k];
 }
 
-/* { dg-final { scan-tree-dump-times "return 1;" 3 "optimized" } } */
+/* The pattern is not applied on ilp32 targets (PR116845).  */
+/* { dg-final { scan-tree-dump-times "return 1;" 3 "optimized" { xfail { ilp32 } } } } */