drm/msm: add extern C guard for the UAPI header

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Acked-by: Rob Clark <robdclark@gmail.com> (over irc)

include/uapi/drm/msm_drm.h

@@ -20,6 +20,10 @@
 
 #include "drm.h"
 
+#if defined(__cplusplus)
+extern "C" {
+#endif
+
 /* Please note that modifications to all structs defined here are
  * subject to backwards-compatibility constraints:
  *  1) Do not use pointers, use __u64 instead for 32 bit / 64 bit
@@ -217,4 +221,8 @@ struct drm_msm_wait_fence {
 #define DRM_IOCTL_MSM_GEM_SUBMIT       DRM_IOWR(DRM_COMMAND_BASE + DRM_MSM_GEM_SUBMIT, struct drm_msm_gem_submit)
 #define DRM_IOCTL_MSM_WAIT_FENCE       DRM_IOW (DRM_COMMAND_BASE + DRM_MSM_WAIT_FENCE, struct drm_msm_wait_fence)
 
+#if defined(__cplusplus)
+}
+#endif
+
 #endif /* __MSM_DRM_H__ */