newlib/libc/sys/rtems/include/machine/param.h: Add _KERNEL to stop method leakage

The following FreeBSD kernel methods are not in any standard and
prototypes/definitions were leaking into application space:

  + round_page()
  + trunc_page()
  + atop()
  + ptoa()
  + pgtok()

newlib/libc/sys/rtems/include/machine/param.h

@@ -71,6 +71,7 @@
 
 #define	MAXPAGESIZES	1		/* maximum number of supported page sizes */
 
+#ifdef _KERNEL
 /*
  * Mach derived conversion macros
  */
@@ -82,4 +83,6 @@
 
 #define	pgtok(x)		((unsigned long)(x) * (PAGE_SIZE / 1024))
 
+#endif
+
 #endif /* !_MACHINE_PARAM_H_ */