Remove ARM/MIPS fenv duplication.

Bug: http://b/32709207
Test: ran tests
Change-Id: I58d354e9f8b1e6023427ba271bf39e4e24b7f8ab
diff --git a/libc/include/bits/fenv_mips.h b/libc/include/bits/fenv_mips.h
index 9298e86..dafccac 100644
--- a/libc/include/bits/fenv_mips.h
+++ b/libc/include/bits/fenv_mips.h
@@ -68,8 +68,7 @@
  * 11 - rounding (down)toward minus infinity (RM)
  */
 
-#ifndef _BITS_FENV_MIPS_H_
-#define _BITS_FENV_MIPS_H_
+#pragma once
 
 #include <sys/types.h>
 
@@ -94,5 +93,3 @@
 #define FE_DOWNWARD   0x0003
 
 __END_DECLS
-
-#endif