gbsim: add missing copyright notice in gbsim.h
gbsim: add missing copyright notice in gbsim.h

Missed the copyright notice in one file, fix that.

Signed-off-by: Matt Porter <c1d287ff3802a4aab0e3770389ea24a33314618b@linaro.org>

bcousson/gbsim,gregkh/gbsim,bcousson/gbsim,bcousson/gbsim,projectara/gbsim,ohporter/gbsim,projectara/gbsim,gregkh/gbsim