Add missing libc++ includes

Bug: 175635923
Test: m MODULES-IN-hardware-interfaces-automotive-can
Change-Id: I2fcc511f45d87b0ca6d80d18df2ba9f92e0155f9
diff --git a/automotive/can/1.0/default/CanSocket.h b/automotive/can/1.0/default/CanSocket.h
index fd956b5..f3e8e60 100644
--- a/automotive/can/1.0/default/CanSocket.h
+++ b/automotive/can/1.0/default/CanSocket.h
@@ -22,6 +22,7 @@
 
 #include <atomic>
 #include <chrono>
+#include <functional>
 #include <thread>
 
 namespace android::hardware::automotive::can::V1_0::implementation {