Don't declare a parameter as const

Whether a parameter should be const is an implementation detail of the
function, so don't declare a parameter of psa_hash_compare as
const. (This only applies to parameters themselves, not to objects
that pointer parameters points to.)
diff --git a/include/psa/crypto.h b/include/psa/crypto.h
index 9c61083..3522818 100644
--- a/include/psa/crypto.h
+++ b/include/psa/crypto.h
@@ -932,7 +932,7 @@
                               const uint8_t *input,
                               size_t input_length,
                               const uint8_t *hash,
-                              const size_t hash_length);
+                              size_t hash_length);
 
 /** The type of the state data structure for multipart hash operations.
  *