drm_hwcomposer: move header files into source directory

... to improve navigation between source/header file.
Unnecessary dependencies also removed.

Signed-off-by: Roman Stratiienko <r.stratiienko@gmail.com>
Change-Id: I2c3bf993b8c5f356490433fd94e90011487a1276
diff --git a/platform/platform.cpp b/platform/platform.cpp
index b7a47c7..9fb91e7 100644
--- a/platform/platform.cpp
+++ b/platform/platform.cpp
@@ -17,10 +17,11 @@
 #define LOG_TAG "hwc-platform"
 
 #include "platform.h"
-#include "drmdevice.h"
 
 #include <log/log.h>
 
+#include "drm/drmdevice.h"
+
 namespace android {
 
 std::vector<DrmPlane *> Planner::GetUsablePlanes(