dt-bindings: pil: Add a new qcom,signal-aop property

Add a new property "qcom,signal-aop" which is used to signal AOP
if a subsystem is brought out of reset.

Change-Id: I163669a424fa710097d8629626eed001bbe809b1
Signed-off-by: Runmin Wang <runminw@codeaurora.org>