POSIX: Enabled hrt queued work to be run

In STM32, the ISR handler calls hrt_call_invoke(). There is no
interrupt timer inthe POSIX port so a work item is put on the
high priority work queue to expire at the next event (in ticks)
or at the next max delay interval.

Counter wrapping is likely still not handled properly in this code.

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

src/platforms/posix/px4_layer/px4_posix_impl.cpp

@@ -51,6 +51,8 @@ __BEGIN_DECLS
 
 long PX4_TICKS_PER_SEC = sysconf(_SC_CLK_TCK);
 
+extern void hrt_init(void);
+
 __END_DECLS
 
 extern struct wqueue_s gwork[NWORKERS];
@@ -78,6 +80,7 @@ void init(int argc, char *argv[], const char *app_name)
 			       work_lpthread,
 			       (char* const*)NULL);
 
+	hrt_init();
 }
 
 }