Fix arm/arm64 <fenv.h> to match current reality.

ARM stopped supporting enabling of FP exceptions years ago.

Bug: http://b/68832485
Test: ran tests
Change-Id: I8450baa78e04d994c352180975b0a1ecd5a9f662
diff --git a/libc/include/fenv.h b/libc/include/fenv.h
index 4276e87..2b607f5 100644
--- a/libc/include/fenv.h
+++ b/libc/include/fenv.h
@@ -32,9 +32,7 @@
 
 #include <sys/cdefs.h>
 
-#if defined(__aarch64__)
-#include <bits/fenv_arm64.h>
-#elif defined(__arm__)
+#if defined(__aarch64__) || defined(__arm__)
 #include <bits/fenv_arm.h>
 #elif defined(__i386__)
 #include <bits/fenv_x86.h>