Add wrapper header file nvgpu/circ_buf.h. It #includes <linux/circ_buf.h> in Linux. JIRA NVGPU-13 Change-Id: I58da6340a6f558cf5678ac6ce91f7fd7fd2dae7e Signed-off-by: Deepak Nibade <dnibade@nvidia.com> Reviewed-on: http://git-master/r/1466657 Reviewed-by: svccoveritychecker <svccoveritychecker@nvidia.com> Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com> GVS: Gerrit_Virtual_Submit Reviewed-by: Bharat Nihalani <bnihalani@nvidia.com>