tile: default to little endian on older toolchains

Older toolchains may not specify __LITTLE_ENDIAN__, but older
toolchains were all little endian.  Don't make things unnecessarily
hard for those toolchains.
Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>

arch/tile/include/uapi/asm/byteorder.h

@@ -14,8 +14,6 @@
 
 #if defined (__BIG_ENDIAN__)
 #include <linux/byteorder/big_endian.h>
-#elif defined (__LITTLE_ENDIAN__)
-#include <linux/byteorder/little_endian.h>
 #else
-#error "__BIG_ENDIAN__ or __LITTLE_ENDIAN__ must be defined."
+#include <linux/byteorder/little_endian.h>
 #endif