Fix aarch64 custom assembler now non-uapi is gone.

Change-Id: I9c8ad17d9bae2de9d793444d87d4ee133728e900
diff --git a/libc/arch-aarch64/bionic/vfork.S b/libc/arch-aarch64/bionic/vfork.S
index 964f38d..7235283 100644
--- a/libc/arch-aarch64/bionic/vfork.S
+++ b/libc/arch-aarch64/bionic/vfork.S
@@ -26,9 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#include <asm/unistd.h>
-#include <linux/err.h>
-#include <machine/asm.h>
+#include <private/bionic_asm.h>
 
 ENTRY(vfork)
     mov     x0, #0x4111     /* CLONE_VM | CLONE_VFORK | SIGCHLD */