Revert "Merge pull request #1399 from mazimkhan/feature-opaque-keys"

This reverts commit 31a24b8d0c084fc7632c4c3cc47a1fc92dcfa75f, reversing
changes made to b3411e57654613f4ca79cc8699d1c270bebdad46.
diff --git a/library/sha512.c b/library/sha512.c
index 4d43487..97cee07 100644
--- a/library/sha512.c
+++ b/library/sha512.c
@@ -277,7 +277,6 @@
 
     return( 0 );
 }
-#endif /* !MBEDTLS_SHA512_PROCESS_ALT */
 
 #if !defined(MBEDTLS_DEPRECATED_REMOVED)
 void mbedtls_sha512_process( mbedtls_sha512_context *ctx,
@@ -286,6 +285,7 @@
     mbedtls_internal_sha512_process( ctx, data );
 }
 #endif
+#endif /* !MBEDTLS_SHA512_PROCESS_ALT */
 
 /*
  * SHA-512 process buffer