x86/entry/64: Use syscall wrappers for x32_rt_sigreturn

Add missing syscall wrapper for x32_rt_sigreturn().

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200313195144.164260-6-brgerst@gmail.com

diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 8a29573..8609049 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -859,7 +859,7 @@ void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
 }
 
 #ifdef CONFIG_X86_X32_ABI
-asmlinkage long sys32_x32_rt_sigreturn(void)
+COMPAT_SYSCALL_DEFINE0(x32_rt_sigreturn)
 {
 	struct pt_regs *regs = current_pt_regs();
 	struct rt_sigframe_x32 __user *frame;