drm_hwcomposer: Move ValidatePlane method into DrmPlane

It is more common to validate the layer for the proper object.

Signed-off-by: Matvii Zorin <matvii.zorin@globallogic.com>
diff --git a/drm/DrmPlane.h b/drm/DrmPlane.h
index 2e2c121..862a0f3 100644
--- a/drm/DrmPlane.h
+++ b/drm/DrmPlane.h
@@ -24,6 +24,7 @@
 
 #include "DrmCrtc.h"
 #include "DrmProperty.h"
+#include "drmhwcomposer.h"
 
 namespace android {
 
@@ -40,6 +41,7 @@
   uint32_t id() const;
 
   bool GetCrtcSupported(const DrmCrtc &crtc) const;
+  bool IsValidForLayer(DrmHwcLayer *layer);
 
   uint32_t type() const;