Remove scary-looking printf output that happens when you kldload dtrace on

arm.  Replace it with a comment block explaining why the function is empty
on 32-bit arm.

sys/cddl/dev/dtrace/arm/dtrace_subr.c

@@ -123,7 +123,18 @@ dtrace_invop_remove(int (*func)(uintptr_t, struct trapframe *, uintptr_t))
 void
 dtrace_toxic_ranges(void (*func)(uintptr_t base, uintptr_t limit))
 {
-	printf("IMPLEMENT ME: dtrace_toxic_ranges\n");
+
+	/*
+	 * There are no ranges to exclude that are common to all 32-bit arm
+	 * platforms.  This function only needs to exclude ranges "... in
+	 * which it is impossible to recover from such a load after it has been
+	 * attempted." -- i.e., accessing within the range causes some sort
+	 * fault in the system which is not handled by the normal arm
+	 * exception-handling mechanisms.  If systems exist where that is the
+	 * case, a method to handle this functionality would have to be added to
+	 * the platform_if interface so that those systems could provide their
+	 * specific toxic range(s).
+	 */
 }
 
 void