Uniformize endianness definition.

diff --git a/include/basetsd.h b/include/basetsd.h
index a481b09..ad8404a 100644
--- a/include/basetsd.h
+++ b/include/basetsd.h
@@ -147,8 +147,8 @@
 # define BITFIELDS_BIGENDIAN
 # undef  ALLOW_UNALIGNED_ACCESS
 #elif defined(__ALPHA__)
-# define WORDS_LITTLEENDIAN
-# define BITFIELDS_LITTLEENDIAN
+# undef  WORDS_BIGENDIAN
+# undef  BITFIELDS_BIGENDIAN
 # undef  ALLOW_UNALIGNED_ACCESS
 #elif !defined(RC_INVOKED) && !defined(__WIDL__)
 # error Unknown CPU architecture!