ACPICA: iASL: Update to use internal acpi_ut_strtoul64 function

ACPICA commit e959584d23b520c53700e90282312d17b9603ed5

Was using a local Strtoul64, update to use the common acpi_ut_strtoul64
and remove the local Strtoul64.

Link: https://github.com/acpica/acpica/commit/e959584d
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>