libata-acpi: allow _GTF on SATA, but disable on PATA for now

The ACPI specification states, and BIOS implementations depend on,
_STM being called before _GTF.

SATA does this, but PATA does not.  So for now, simply
prevent execution of _GTF on PATA devices.  Longer term we
should implement ACPI support for PATA devices in libata.

Signed-off-by: Kristen Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>