Keep track of remaining fd when devices are removed

Sometimes the wrong fd was accessed when the device was addressed
by device id.

The earlier implementation assumed that two arrays were in sync
but one of them was compacted when devices were removed. Instead
of that dependency the device now keeps track of it's file descriptor.

Change-Id: Ib0f320603aafb07ded354bc3687de9759c9068f2
diff --git a/include/ui/EventHub.h b/include/ui/EventHub.h
index 3132941..3d42856 100644
--- a/include/ui/EventHub.h
+++ b/include/ui/EventHub.h
@@ -224,6 +224,7 @@
         uint8_t*        keyBitmask;
         KeyLayoutMap*   layoutMap;
         String8         keylayoutFilename;
+        int             fd;
         device_t*       next;
         
         device_t(int32_t _id, const char* _path, const char* name);