Bring our <machine/endian.h> files back in sync.

They'd drifted slightly which led to a compilation error in toybox,
which was assuming pid_t was defined. arm and arm64 were picking it
up via <endian.h> but x86 wasn't.

Change-Id: I58401e6c0066959dfc3b305b020876aaf7074bbf

libc/arch-mips64/include/machine/endian.h

@@ -58,11 +58,7 @@
 #endif  /* __mips32r2__ */
 #endif  /* __GNUC__ */
 
-#if defined(__MIPSEB__)
-#define _BYTE_ORDER _BIG_ENDIAN
-#else
 #define _BYTE_ORDER _LITTLE_ENDIAN
-#endif
 #define __STRICT_ALIGNMENT
 #include <sys/types.h>
 #include <sys/endian.h>