Predicate can be used for an implicit return value.
This change improves the implicit return mechanism to be more
compatible with the MS interpreter.

http://www.acpica.org/bugzilla/show_bug.cgi?id=349

Below AML code from http://bugzilla.kernel.org/show_bug.cgi?id=10686

	Store(0x07D6, OSYS)
	Method (_CRT, 0, Serialized)
	{
	    If (LLess (OSYS, 0x07D6))
	    {
		If (LEqual (\_SB.TJ85, Zero))
		{
		    Return (Add (0x0AAC, Multiply (TPC, 0x0A)))
		}
		Else
		{
		    Return (Add (0x0AAC, Multiply (TP85, 0x0A)))
		}
	    }
	}

Previously _CRT returns 0x07D6, now it returns 0 (predicate value of LLess)
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>