consolidate cond_syscall and SYSCALL_ALIAS declarations

take them to asm/linkage.h, with default in linux/linkage.h

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

include/asm-generic/unistd.h

@@ -9,20 +9,3 @@
 #define __ARCH_WANT_STAT64
 #define __ARCH_WANT_SYS_LLSEEK
 #endif
-
-/*
- * "Conditional" syscalls
- *
- * What we want is __attribute__((weak,alias("sys_ni_syscall"))),
- * but it doesn't work on all toolchains, so we just do it by hand
- */
-#ifndef cond_syscall
-#ifdef CONFIG_SYMBOL_PREFIX
-#define __SYMBOL_PREFIX CONFIG_SYMBOL_PREFIX
-#else
-#define __SYMBOL_PREFIX
-#endif
-#define cond_syscall(x) asm(".weak\t" __SYMBOL_PREFIX #x "\n\t" \
-			    ".set\t" __SYMBOL_PREFIX #x "," \
-			    __SYMBOL_PREFIX "sys_ni_syscall")
-#endif