Use safer size for tag checking

Signed-off-by: Paul Elliott <paul.elliott@arm.com>
diff --git a/library/psa_crypto_driver_wrappers.c b/library/psa_crypto_driver_wrappers.c
index 5e7eb11..4c56162 100644
--- a/library/psa_crypto_driver_wrappers.c
+++ b/library/psa_crypto_driver_wrappers.c
@@ -1749,7 +1749,7 @@
                                                   plaintext_size,
                                                   plaintext_length,
                                                   check_tag,
-                                                  tag_length,
+                                                  sizeof( check_tag ),
                                                   &check_tag_length );
 
                 if( status == PSA_SUCCESS )