POSIX: Fixes for HRT implementation of simulated HW clock polling

There is a race condition for the accel and mag polling rates.
Whichever one gets set first, the other will be uninitialized.

Set the mag polling rate to 1ms if uninitilized.

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

src/platforms/posix/px4_layer/module.mk

@@ -38,6 +38,9 @@
 SRCS		 = 	\
 			px4_posix_impl.cpp \
 			px4_posix_tasks.cpp  \
+			hrt_thread.c \
+			hrt_queue.c \
+			hrt_work_cancel.c \
 			work_thread.c \
 			work_queue.c \
 			work_cancel.c \