Release SurfaceControl after creating an input channel

During the input channel creation we are passing a SurfaceControl object to
SystemServer. Holding on to the SurfaceControl in the app extends the lifetime of the SurfaceControl and relies on GC to clean up the last reference.

Bug: 436302937
Flag: EXEMPT bug fix
Test: presubmit
Change-Id: I9cb57171980f356ee67122b0045b28e3bbf7ef21