binder: Don't use reinterpret_cast to down cast

In general, reinterpret_cast could do the wrong thing, e.g. if a class
derived from Parcelable and added more virtual methods, then the
pointer value needs to be adjusted when down casting.

Test: TH
Change-Id: I0d808cafa7501e9d03b83a03d1de9219bc672912
1 file changed