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. Predefined names: Add support for the _PRP method.
 2. Update for _PRP predefined name.
 3. Add support for _LPD and _PRP methods.
 4. iASL: Add check for _PRP/_HID dependency, with error message.

Signed-off-by: Lv Zheng <lv.zheng@intel.com>