x86, mm, kprobes: fault.c, simplify notify_page_fault()

Impact: cleanup

Remove an #ifdef from notify_page_fault(). The function still
compiles to nothing in the !CONFIG_KPROBES case.

Introduce kprobes_built_in() and kprobe_fault_handler() helpers
to allow this - they returns 0 if !CONFIG_KPROBES.

No code changed:

   text	   data	    bss	    dec	    hex	filename
   4618	     32	     24	   4674	   1242	fault.o.before
   4618	     32	     24	   4674	   1242	fault.o.after

Cc: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index fe99af4..379beae 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -68,11 +68,10 @@
 
 static inline int notify_page_fault(struct pt_regs *regs)
 {
-#ifdef CONFIG_KPROBES
 	int ret = 0;
 
 	/* kprobe_running() needs smp_processor_id() */
-	if (!user_mode_vm(regs)) {
+	if (kprobes_built_in() && !user_mode_vm(regs)) {
 		preempt_disable();
 		if (kprobe_running() && kprobe_fault_handler(regs, 14))
 			ret = 1;
@@ -80,9 +79,6 @@
 	}
 
 	return ret;
-#else
-	return 0;
-#endif
 }
 
 /*