Switch the rest of our internal headers to #pragma once.

We've been using #pragma once for new internal files, but let's be more bold.

Bug: N/A
Test: builds
Change-Id: I7e2ee2730043bd884f9571cdbd8b524043030c07
diff --git a/libc/bionic/bionic_netlink.h b/libc/bionic/bionic_netlink.h
index bc0e3f0..a21200e 100644
--- a/libc/bionic/bionic_netlink.h
+++ b/libc/bionic/bionic_netlink.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef BIONIC_NETLINK_H
-#define BIONIC_NETLINK_H
+#pragma once
 
 #include <sys/types.h>
 
@@ -49,5 +48,3 @@
   char* data_;
   size_t size_;
 };
-
-#endif