moves tx_timer interrupt into port

as this is not moonlight specific, it should not be placed in such a way

port/threadx/CMakeLists.txt

@@ -9,8 +9,7 @@ target_sources(${PROJECT_NAME}
     ${CMAKE_CURRENT_LIST_DIR}/src/tx_thread_schedule.S
     ${CMAKE_CURRENT_LIST_DIR}/src/tx_thread_stack_build.S
     ${CMAKE_CURRENT_LIST_DIR}/src/tx_thread_system_return.S
-    #${CMAKE_CURRENT_LIST_DIR}/src/tx_timer_interrupt.c
-    #${CMAKE_CURRENT_LIST_DIR}/src/platform_rand.c
+    ${CMAKE_CURRENT_LIST_DIR}/src/tx_timer_interrupt.c
     # {{END_TARGET_SOURCES}}
 )