Add NT_PRSTATUS to <elf.h>.

Needed by aarch64.

Bug: 12476126
Change-Id: I7764664459a06cf4f2a60e707bd968d321a78430
diff --git a/linker/linker.h b/linker/linker.h
index 647c36a..9afd9e1 100644
--- a/linker/linker.h
+++ b/linker/linker.h
@@ -29,12 +29,9 @@
 #ifndef _LINKER_H_
 #define _LINKER_H_
 
-#include <unistd.h>
-#include <sys/types.h>
 #include <elf.h>
-#include <sys/exec_elf.h>
-
 #include <link.h>
+#include <unistd.h>
 
 #include "private/libc_logging.h"