drm_hwcomposer: Add include guard into drmhwctwo.h

Include guard was missed for the file.

Signed-off-by: Matvii Zorin <matvii.zorin@globallogic.com>
diff --git a/include/drmhwctwo.h b/include/drmhwctwo.h
index 1f226bc..62ee85a 100644
--- a/include/drmhwctwo.h
+++ b/include/drmhwctwo.h
@@ -14,6 +14,9 @@
  * limitations under the License.
  */
 
+#ifndef ANDROID_DRM_HWC_TWO_H_
+#define ANDROID_DRM_HWC_TWO_H_
+
 #include "drmdisplaycompositor.h"
 #include "drmhwcomposer.h"
 #include "platform.h"
@@ -370,3 +373,5 @@
   std::string mDumpString;
 };
 }  // namespace android
+
+#endif