Use -1.0f in SurfaceControl to turn off brightness

-1.0f is sent to SurfaceControl if the brightess is equal to 0.
0 was originally used; -1.0f is being used in preparation for using floating
point brightness in the whole framework.

Test: Manual
Bug: b/139959979
Change-Id: I7d72a8c39d1c225ea9c2a2651366111df3be355d