aarch64: Adjust tests after fix for PR102659

aarch64: Adjust tests after fix for PR102659

After the fix for PR102659, the vectoriser can no longer group
conditional accesses of the form:

  for (int i = 0; i < n; ++i)
    if (...)
      ...a[i * 2] + a[i * 2 + 1]...;

on LP64 targets.  It has to treat them as two independent
gathers instead.

This was causing failures in the sve mask_struct*.c tests.
The tests weren't really testing that int iterators could
be used, so this patch switches to pointer-sized iterators
instead.

gcc/testsuite/
	* gcc.target/aarch64/sve/mask_struct_load_1.c: Use intptr_t
	iterators instead of int iterators.
	* gcc.target/aarch64/sve/mask_struct_load_2.c: Likewise.
	* gcc.target/aarch64/sve/mask_struct_load_3.c: Likewise.
	* gcc.target/aarch64/sve/mask_struct_load_4.c: Likewise.
	* gcc.target/aarch64/sve/mask_struct_load_5.c: Likewise.
	* gcc.target/aarch64/sve/mask_struct_load_6.c: Likewise.
	* gcc.target/aarch64/sve/mask_struct_load_7.c: Likewise.
	* gcc.target/aarch64/sve/mask_struct_load_8.c: Likewise.
	* gcc.target/aarch64/sve/mask_struct_store_1.c: Likewise.
	* gcc.target/aarch64/sve/mask_struct_store_2.c: Likewise.
	* gcc.target/aarch64/sve/mask_struct_store_3.c: Likewise.
	* gcc.target/aarch64/sve/mask_struct_store_4.c: Likewise.