fixup x86 setdomainname.S

Both be910529322b461148debefd50b9e0d67ae84f8e and
e2faf07d659b1c824002e50b9cdfa9caae62a31b were submitted about
two days ago. The former changed how the syscalls stubs were
generated, but the latter was submitted using the old stub
format.

Use the new stub format for setdomainname.S

Change-Id: I578acd7053f57a275f6831dd2404ef04826c578e
diff --git a/libc/arch-x86/syscalls/setdomainname.S b/libc/arch-x86/syscalls/setdomainname.S
index 57189fe..8b6afe2 100644
--- a/libc/arch-x86/syscalls/setdomainname.S
+++ b/libc/arch-x86/syscalls/setdomainname.S
@@ -9,10 +9,18 @@
     pushl   %ecx
     .cfi_adjust_cfa_offset 4
     .cfi_rel_offset ecx, 0
-    mov     12(%esp), %ebx
-    mov     16(%esp), %ecx
+
+    call    __kernel_syscall
+    pushl   %eax
+    .cfi_adjust_cfa_offset 4
+    .cfi_rel_offset eax, 0
+
+    mov     16(%esp), %ebx
+    mov     20(%esp), %ecx
     movl    $__NR_setdomainname, %eax
-    int     $0x80
+    call    *(%esp)
+    addl    $4, %esp
+
     cmpl    $-MAX_ERRNO, %eax
     jb      1f
     negl    %eax