syscalls: add sys_ni_posix_timers prototype

The sys_ni_posix_timers() definition causes a warning when the declaration
is missing, so this needs to be added along with the normal syscalls,
outside of the #ifdef.

kernel/time/posix-stubs.c:26:17: error: no previous prototype for 'sys_ni_posix_timers' [-Werror=missing-prototypes]

Link: https://lkml.kernel.org/r/20230607142925.3126422-1-arnd@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

arch/alpha/kernel/osf_sys.c

@@ -1014,8 +1014,6 @@ SYSCALL_DEFINE2(osf_settimeofday, struct timeval32 __user *, tv,
 	return do_sys_settimeofday64(tv ? &kts : NULL, tz ? &ktz : NULL);
 }
 
-asmlinkage long sys_ni_posix_timers(void);
-
 SYSCALL_DEFINE2(osf_utimes, const char __user *, filename,
 		struct timeval32 __user *, tvs)
 {

include/linux/syscalls.h

@@ -1280,6 +1280,7 @@ asmlinkage long sys_ni_syscall(void);
 
 #endif /* CONFIG_ARCH_HAS_SYSCALL_WRAPPER */
 
+asmlinkage long sys_ni_posix_timers(void);
 
 /*
  * Kernel code should not call syscalls (i.e., sys_xyzyyz()) directly.

kernel/time/posix-stubs.c

@@ -16,6 +16,7 @@
 #include <linux/posix-timers.h>
 #include <linux/time_namespace.h>
 #include <linux/compat.h>
+#include <linux/syscalls.h>
 
 #ifdef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
 /* Architectures may override SYS_NI and COMPAT_SYS_NI */