sim/posix: move rt_hw_context_switch_interrupt after it's definition

This fix a compile error in Clang.

libcpu/sim/posix/cpu_port.c

@@ -363,12 +363,6 @@ void rt_hw_interrupt_enable(rt_base_t level)
     /*TODO: It may need to unmask the signal */
 }
 
-void rt_hw_context_switch_interrupt(rt_uint32_t from,
-                                    rt_uint32_t to)
-{
-    rt_hw_context_switch(from, to);
-}
-
 void rt_hw_context_switch(rt_uint32_t from,
                           rt_uint32_t to)
 {
@@ -400,6 +394,12 @@ void rt_hw_context_switch(rt_uint32_t from,
     pthread_mutex_unlock(ptr_int_mutex);
 }
 
+void rt_hw_context_switch_interrupt(rt_uint32_t from,
+                                    rt_uint32_t to)
+{
+    rt_hw_context_switch(from, to);
+}
+
 void rt_hw_context_switch_to(rt_uint32_t to)
 {
     //set to thread