remove comment cruft that got left behind in x86_64 syscall.s

src/internal/x86_64/syscall.s

@@ -1,7 +1,6 @@
 .global __syscall
 .type __syscall,%function
 __syscall:
-di,si,dx,cx,r8,r9
 	movq %rdi,%rax
 	movq %rsi,%rdi
 	movq %rdx,%rsi