ftrace: Mark get_lock_parent_ip() __always_inline

If the compiler decides not to inline this function then preemption
tracing will always show an IP inside the preemption disabling path and
never the function actually calling preempt_{enable,disable}.

Link: https://lore.kernel.org/linux-trace-kernel/20230327173647.1690849-1-john@metanate.com

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: stable@vger.kernel.org
Fixes: f904f582 ("sched/debug: Fix preempt_disable_ip recording for preempt_disable()")
Signed-off-by: John Keeping <john@metanate.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

include/linux/ftrace.h

@@ -980,7 +980,7 @@ static inline void __ftrace_enabled_restore(int enabled)
 #define CALLER_ADDR5 ((unsigned long)ftrace_return_address(5))
 #define CALLER_ADDR6 ((unsigned long)ftrace_return_address(6))
 
-static inline unsigned long get_lock_parent_ip(void)
+static __always_inline unsigned long get_lock_parent_ip(void)
 {
 	unsigned long addr = CALLER_ADDR0;