psa: Fix unused variable warnings

Fix unused variable warnings when no AEAD
algorithm is enabled in the build.

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
diff --git a/library/psa_crypto_aead.c b/library/psa_crypto_aead.c
index c7f7352..03327f2 100644
--- a/library/psa_crypto_aead.c
+++ b/library/psa_crypto_aead.c
@@ -432,7 +432,9 @@
     else
 #endif /* MBEDTLS_PSA_BUILTIN_ALG_CHACHA20_POLY1305 */
     {
+        ( void ) operation;
         ( void ) nonce;
+        ( void ) nonce_length;
 
         return ( PSA_ERROR_NOT_SUPPORTED );
     }
@@ -533,8 +535,10 @@
     else
 #endif /* MBEDTLS_PSA_BUILTIN_ALG_CHACHA20_POLY1305 */
     {
+        ( void ) operation;
         ( void ) input;
-        ( void ) input_length;
+        ( void ) output;
+        ( void ) output_size;
 
         return ( PSA_ERROR_NOT_SUPPORTED );
     }