ACPICA: Update internal namespace node/handle interfaces

This change deletes the unnecessary acpi_ns_convert_entry_to_handle
interface and renames the acpi_ns_map_handle_to_node interface to
acpi_ns_validate_handle.  ACPICA BZ 798.

http://www.acpica.org/bugzilla/show_bug.cgi?id=798



Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>