[PATCH 1/7] um: Fix -Wmissing-prototypes warnings for (rt_)sigreturn

["Tiwei Bie" <tiwei.btw@antgroup.com>]

Use SYSCALL_DEFINE0 to define (rt_)sigreturn. This will address
below -Wmissing-prototypes warnings:

arch/x86/um/signal.c:453:6: warning: no previous prototype for ‘sys_sigreturn’ [-Wmissing-prototypes]
arch/x86/um/signal.c:560:6: warning: no previous prototype for ‘sys_rt_sigreturn’ [-Wmissing-prototypes]

Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
---
 arch/x86/um/signal.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/um/signal.c b/arch/x86/um/signal.c
index 263e1d08f216..48e87b45adba 100644
--- a/arch/x86/um/signal.c
+++ b/arch/x86/um/signal.c
@@ -8,6 +8,7 @@
 #include <linux/personality.h>
 #include <linux/ptrace.h>
 #include <linux/kernel.h>
+#include <linux/syscalls.h>
 #include <asm/unistd.h>
 #include <linux/uaccess.h>
 #include <asm/ucontext.h>
@@ -450,7 +451,7 @@ int setup_signal_stack_si(unsigned long stack_top, struct ksignal *ksig,
 	return 0;
 }
 
-long sys_sigreturn(void)
+SYSCALL_DEFINE0(sigreturn)
 {
 	unsigned long sp = PT_REGS_SP(&current->thread.regs);
 	struct sigframe __user *frame = (struct sigframe __user *)(sp - 8);
@@ -557,7 +558,7 @@ int setup_signal_stack_si(unsigned long stack_top, struct ksignal *ksig,
 }
 #endif
 
-long sys_rt_sigreturn(void)
+SYSCALL_DEFINE0(rt_sigreturn)
 {
 	unsigned long sp = PT_REGS_SP(&current->thread.regs);
 	struct rt_sigframe __user *frame =
-- 
2.34.1