Update includes to to be relative to src directory

Don't use relative imports like `../foo.h` as those depend on the
relative position of both files. Rather than that use imports relative
to the `src` directory, which explicitly is part of the include
directories.

src/logging/DummyLogger.h

@@ -1,5 +1,5 @@
 #pragma once
-#include "Logger.h"
+#include "logging/Logger.h"
 
 namespace Pinetime {
   namespace Logging {

src/logging/NrfLogger.cpp

@@ -1,4 +1,4 @@
-#include "NrfLogger.h"
+#include "logging/NrfLogger.h"
 
 #include <libraries/log/nrf_log.h>
 #include <libraries/log/nrf_log_ctrl.h>

src/logging/NrfLogger.h

@@ -1,5 +1,5 @@
 #pragma once
-#include "Logger.h"
+#include "logging/Logger.h"
 
 #include <FreeRTOS.h>
 #include <task.h>