pk: fix description of mbedtls_pk_setup_opaque for sign_ext()
Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/include/mbedtls/pk.h b/include/mbedtls/pk.h
index 86ab7d6..e33702f 100644
--- a/include/mbedtls/pk.h
+++ b/include/mbedtls/pk.h
@@ -369,7 +369,9 @@
* * EC:
* * verify, verify_ext, sign, sign_ext: ECDSA.
* * RSA:
- * * sign, sign_ext, decrypt: use the primary algorithm in the wrapped PSA key;
+ * * sign, decrypt: use the primary algorithm in the wrapped PSA key;
+ * * sign_ext: RSA PSS if the pk_type is #MBEDTLS_PK_RSASSA_PSS, otherwise
+ * it falls back to the sign() case;
* * verify, verify_ext, encrypt: not supported.
*
* In order for the above operations to succeed, the policy of the wrapped PSA