kprobes: Fix compiler warning for !CONFIG_KPROBES_ON_FTRACE

Fix compiler warning(as show below) for !CONFIG_KPROBES_ON_FTRACE.

kernel/kprobes.c: In function 'kill_kprobe':
kernel/kprobes.c:1116:33: warning: statement with no effect
[-Wunused-value]
 1116 | #define disarm_kprobe_ftrace(p) (-ENODEV)
      |                                 ^
kernel/kprobes.c:2154:3: note: in expansion of macro
'disarm_kprobe_ftrace'
 2154 |   disarm_kprobe_ftrace(p);

Link: https://lore.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]

Reported-by: Stephen Rothwell <[email protected]>
Fixes: 0cb2f13 ("kprobes: Fix NULL pointer dereference at kprobe_ftrace_handler")
Acked-by: Masami Hiramatsu <[email protected]>
Acked-by: John Fastabend <[email protected]>
Signed-off-by: Muchun Song <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>

Author: Muchun Song

kernel/kprobes.c

@@ -1079,9 +1079,20 @@ static int disarm_kprobe_ftrace(struct kprobe *p)
 		ipmodify ? &kprobe_ipmodify_enabled : &kprobe_ftrace_enabled);
 }
 #else	/* !CONFIG_KPROBES_ON_FTRACE */
-#define prepare_kprobe(p)	arch_prepare_kprobe(p)
-#define arm_kprobe_ftrace(p)	(-ENODEV)
-#define disarm_kprobe_ftrace(p)	(-ENODEV)
+static inline int prepare_kprobe(struct kprobe *p)
+{
+	return arch_prepare_kprobe(p);
+}
+
+static inline int arm_kprobe_ftrace(struct kprobe *p)
+{
+	return -ENODEV;
+}
+
+static inline int disarm_kprobe_ftrace(struct kprobe *p)
+{
+	return -ENODEV;
+}
 #endif
 
 /* Arm a kprobe with text_mutex */