chan_dahdi: wrap include file which is not present on BSD systems in #ifdef

The sys/sysmacros.h include file does not exist in BSD systems and
is not required to build this module there.
Since an "#if defined(__NetBSD__) || defined(__FreeBSD__)" section
already exist I moved that include line inside it's #else branch.

ASTERISK-27343 #close

Change-Id: Ibfb64f4e9a0ce8b6eda7a7695cfe57916f175dc1

channels/chan_dahdi.c

@@ -56,11 +56,12 @@
 
 #if defined(__NetBSD__) || defined(__FreeBSD__)
 #include <pthread.h>
+#else
+#include <sys/sysmacros.h>
 #endif
 #include <signal.h>
 #include <sys/stat.h>
 #include <math.h>
-#include <sys/sysmacros.h>
 
 #include "sig_analog.h"
 /* Analog signaling is currently still present in chan_dahdi for use with