ACPICA: Namespace: Remove _PRP method support.

The _PRP method is not going to be a part of the ACPI standard. This patch
removes its support code introduced by the following commits:
 1. ACPICA: Predefined names: Add support for the _PRP method.
 2. ACPICA: Update for _PRP predefined name.
 3. ACPICA: Add support for _LPD and _PRP methods.
 4. ACPICA: Back port of _PRP update.

Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>