surface_control: Add missing nullability annotations

The surface control and transaction are barely every null in most calls,
but some informational structures like HDR metadata, and the surface
control when reparenting are allowed to be null.

Change-Id: Ia1a456041daf8136d856a1901881b74f97b3593a
Merged-In: Ia1a456041daf8136d856a1901881b74f97b3593a
Test: make aosp_cf_x86_64_phone
Signed-off-by: Marijn Suijten <marijns95@gmail.com>