Re: [PATCH] powerpc/ptrace: Add prototype for function pt_regs_check

`pt_regs_check` is a dummy function, its purpose is to break the build
if struct pt_regs and struct user_pt_regs don't match.

This function has no functionnal purpose, and will get eliminated at
link time or after init depending on CONFIG_LD_DEAD_CODE_DATA_ELIMINATION

This commit adds a prototype to fix warning at W=1:

  arch/powerpc/kernel/ptrace.c:3339:13: error: no previous prototype for ‘pt_regs_check’ [-Werror=missing-prototypes]

Suggested-by: Christophe Leroy <redacted>
Signed-off-by: Mathieu Malaterre <redacted>
---
 arch/powerpc/kernel/ptrace.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
index a398999d0770..341c0060b4c8 100644
--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c

@@ -3338,6 +3338,10 @@ void do_syscall_trace_leave(struct pt_regs *regs)
        user_enter();
 }

+void __init pt_regs_check(void);
+/* dummy function, its purpose is to break the build if struct pt_regs and
+ * struct user_pt_regs don't match.
+ */