Timing adapter fix, init constructor priority

The timing adapters are attached to the Ethos-U AXI ports and should
only be initialized if the platform has been built with NPU support.

Add priority to init the constructor, insuring it will run before
any other constructor. This is important because the init constructor
sets up UART.

Change-Id: I189687437b95b11f6503c7631720e7883c24ada6
diff --git a/targets/common/src/init.cpp b/targets/common/src/init.cpp
index 54e4590..0876070 100644
--- a/targets/common/src/init.cpp
+++ b/targets/common/src/init.cpp
@@ -18,6 +18,6 @@
 
 #include <target.hpp>
 
-__attribute__((constructor)) void init() {
+__attribute__((constructor(500))) void init() {
     EthosU::targetSetup();
 }