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/linker/linker_main.h b/linker/linker_main.h
index 5641696..8d486e8 100644
--- a/linker/linker_main.h
+++ b/linker/linker_main.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef __LINKER_MAIN_H
-#define __LINKER_MAIN_H
+#pragma once
 
 #include <android/dlext.h>
 
@@ -71,5 +70,3 @@
 bool solist_remove_soinfo(soinfo* si);
 soinfo* solist_get_head();
 soinfo* solist_get_somain();
-
-#endif