sanitize rt_sigaction() situation a bit

Switch from __ARCH_WANT_SYS_RT_SIGACTION to opposite
(!CONFIG_ODD_RT_SIGACTION); the only two architectures that
need it are alpha and sparc.  The reason for use of CONFIG_...
instead of __ARCH_... is that it's needed only kernel-side
and doing it that way avoids a mess with include order on many
architectures.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

include/linux/syscalls.h

@@ -377,6 +377,12 @@ asmlinkage long sys_init_module(void __user *umod, unsigned long len,
 asmlinkage long sys_delete_module(const char __user *name_user,
 				unsigned int flags);
 
+#ifndef CONFIG_ODD_RT_SIGACTION
+asmlinkage long sys_rt_sigaction(int,
+				 const struct sigaction __user *,
+				 struct sigaction __user *,
+				 size_t);
+#endif
 asmlinkage long sys_rt_sigprocmask(int how, sigset_t __user *set,
 				sigset_t __user *oset, size_t sigsetsize);
 asmlinkage long sys_rt_sigpending(sigset_t __user *set, size_t sigsetsize);