frameworks/base: use proper nativehelper headers

libnativehelper exports headers under nativehelper. These were
available before incorrectly as global headers in order to give
access to jni.h.

Test: modules using frameworks/base find headers
Bug: 63762847
Change-Id: I0f9f231acdebe460f279135462f43d3e32eff64d
diff --git a/core/jni/android_os_UEventObserver.cpp b/core/jni/android_os_UEventObserver.cpp
index 30d40a2..2df74b0 100644
--- a/core/jni/android_os_UEventObserver.cpp
+++ b/core/jni/android_os_UEventObserver.cpp
@@ -21,13 +21,13 @@
 
 #include "hardware_legacy/uevent.h"
 #include "jni.h"
-#include "JNIHelp.h"
+#include <nativehelper/JNIHelp.h>
 #include "core_jni_helpers.h"
 
 #include <utils/Mutex.h>
 #include <utils/Vector.h>
 #include <utils/String8.h>
-#include <ScopedUtfChars.h>
+#include <nativehelper/ScopedUtfChars.h>
 
 namespace android {