Chane error code in psa_export_public_key_iop_setup() in case key size is 0

Signed-off-by: Waleed Elmelegy <waleed.elmelegy@arm.com>
diff --git a/tf-psa-crypto/core/psa_crypto.c b/tf-psa-crypto/core/psa_crypto.c
index 827a228..beb17d5 100644
--- a/tf-psa-crypto/core/psa_crypto.c
+++ b/tf-psa-crypto/core/psa_crypto.c
@@ -1730,7 +1730,7 @@
     key_size = PSA_EXPORT_KEY_OUTPUT_SIZE(private_key_type,
                                           psa_get_key_bits(&private_key_attributes));
     if (key_size == 0) {
-        status = PSA_ERROR_INVALID_ARGUMENT;
+        status = PSA_ERROR_NOT_SUPPORTED;
         goto exit;
     }