better support for reverse-endian variants of arm/mips/microblaze

these macros are supported by more compilers

arch/arm/bits/endian.h

@@ -1 +1,5 @@
+#if __ARMEB__
+#define __BYTE_ORDER __BIG_ENDIAN
+#else
 #define __BYTE_ORDER __LITTLE_ENDIAN
+#endif

arch/microblaze/bits/endian.h

@@ -1 +1,5 @@
+#if __MICROBLAZEEL__
+#define __BYTE_ORDER __LITTLE_ENDIAN
+#else
 #define __BYTE_ORDER __BIG_ENDIAN
+#endif

arch/mips/bits/endian.h

@@ -1 +1,5 @@
+#if _MIPSEL || __MIPSEL || __MIPSEL__
+#define __BYTE_ORDER __LITTLE_ENDIAN
+#else
 #define __BYTE_ORDER __BIG_ENDIAN
+#endif