rseq: Always inline rseq_debug_syscall_return()

To get the full benefit of:

  eaa9088 ("rseq: Use static branch for syscall exit debug when GENERIC_IRQ_ENTRY=y")

clang needs an __always_inline instead of a plain inline qualifier:

	$ for i in {1..10}; do taskset -c 4 perf5 bench syscall basic -l 100000000 | grep "ops/sec"; done

		 Before	     After
	ops/sec  1542449    15872221   +2.9%

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://patch.msgid.link/20251205100753.4073221-1-edumazet@google.com

Author: edumazet

include/linux/rseq_entry.h

@@ -596,7 +596,7 @@ static __always_inline void rseq_exit_to_user_mode_legacy(void)
 
 void __rseq_debug_syscall_return(struct pt_regs *regs);
 
-static inline void rseq_debug_syscall_return(struct pt_regs *regs)
+static __always_inline void rseq_debug_syscall_return(struct pt_regs *regs)
 {
 	if (static_branch_unlikely(&rseq_debug_enabled))
 		__rseq_debug_syscall_return(regs);