added a os-agnostic sim.h header which could be included in by any platform, moved out os specific headers to nvgpu/linux. JIRA VQRM-2368 Change-Id: I3861bfa75a6b8d2d909bc7223467fd68c208275b Signed-off-by: Antony Clince Alex <aalex@nvidia.com> Reviewed-on: https://git-master.nvidia.com/r/1702816 Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com> Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>