adb: delete unused members in fdevent.

Forgot to clean this up after removing fdevent_install...

Test: treehugger
Change-Id: I53d21134a4bc8bf7b16210318c6fac5075445b39
diff --git a/adb/fdevent.h b/adb/fdevent.h
index 69c4072..39fa9c2 100644
--- a/adb/fdevent.h
+++ b/adb/fdevent.h
@@ -32,9 +32,6 @@
 typedef void (*fd_func)(int fd, unsigned events, void *userdata);
 
 struct fdevent {
-    fdevent* next = nullptr;
-    fdevent* prev = nullptr;
-
     unique_fd fd;
     int force_eof = 0;