gpu: nvgpu: vgpu: add vgpu_init_hal_os

The goal is to make vgpu_init_hal to be common across OSes, then we can
commonize more functions. OSes have to implement vgpu_init_hal_os. For
linux, it's empty.

Jira GVSCI-82

Change-Id: I6c8263fa884a726a8bec4c57bbf840adb86a8a56
Signed-off-by: Richard Zhao <rizhao@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/1987234
Reviewed-by: svc-mobile-coverity <svc-mobile-coverity@nvidia.com>
Reviewed-by: svc-mobile-misra <svc-mobile-misra@nvidia.com>
Reviewed-by: Aparna Das <aparnad@nvidia.com>
GVS: Gerrit_Virtual_Submit
Reviewed-by: Nirav Patel <nipatel@nvidia.com>
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

drivers/gpu/nvgpu/os/linux/vgpu/vgpu_linux.c

@@ -545,3 +545,8 @@ int vgpu_tegra_resume(struct device *dev)
 
 	return err;
 }
+
+int vgpu_init_hal_os(struct gk20a *g)
+{
+	return 0;
+}