fix typo in x86_64 part of syscall overhaul

arch/x86_64/bits/syscall.h

@@ -43,7 +43,7 @@ static inline long __syscall5(long __n, long __a1, long __a2, long __a3, long __
 {
 	unsigned long __ret;
 	register long __r10 __asm__("r10") = __a4;
-	register long__ r8 __asm__("r8") = __a5;
+	register long __r8 __asm__("r8") = __a5;
 	__asm__ __volatile__ ("syscall" : "=a"(__ret) : "a"(__n), "D"(__a1), "S"(__a2),
 						  "d"(__a3), "r"(__r10), "r"(__r8) : "rcx", "r11", "memory");
 	return __ret;