Make sure that these are set to sane values even on silly tunables:

• There must be at least one thread to process the 'acpi_taskq'.
• Ensure that the maximum number of tasks is at least 0. Setting it to a very low positive number is still silly in practice as it will cause AcpiOSExecute() to fail more often then not, but at least won't cause huge bogus memory allocations when allocating acpi_tasks[].