psd: move defines to user/kernelspace part where possible

Some of these defines have no meaning in userspace, so there
is no need to make those available.

extensions/libxt_psd.c

@@ -30,6 +30,8 @@
 #include "xt_psd.h"
 #include "compat_user.h"
 
+#define SCAN_DELAY_THRESHOLD		300
+
 /* Function which prints out usage message. */
 static void psd_mt_help(void) {
 	printf(