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>

arch/mips/include/asm/linkage.h

@@ -6,5 +6,8 @@
 #endif
 
 #define __weak __attribute__((weak))
+#define cond_syscall(x) asm(".weak\t" #x "\n" #x "\t=\tsys_ni_syscall")
+#define SYSCALL_ALIAS(alias, name)					\
+	asm ( #alias " = " #name "\n\t.globl " #alias)
 
 #endif