Fix an error that caused interrupts to become disabled

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@3724 42af7a65-404d-4744-a932-0658087f49c3

mm/mm_sem.c

@@ -200,7 +200,9 @@ void mm_takesemaphore(void)
 
 void mm_givesemaphore(void)
 {
+#ifdef CONFIG_DEBUG
   pid_t my_pid = getpid();
+#endif
 
   /* I better be holding at least one reference to the semaphore */