Add guards for mbedtls_psa_crypto_free()

Signed-off-by: Przemek Stekiel <przemyslaw.stekiel@mobica.com>
diff --git a/programs/pkey/key_app.c b/programs/pkey/key_app.c
index 82a4de1..2f30830 100644
--- a/programs/pkey/key_app.c
+++ b/programs/pkey/key_app.c
@@ -284,7 +284,9 @@
 #endif
 
     mbedtls_pk_free(&pk);
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
     mbedtls_psa_crypto_free();
+#endif /* MBEDTLS_USE_PSA_CRYPTO */
     mbedtls_mpi_free(&N); mbedtls_mpi_free(&P); mbedtls_mpi_free(&Q);
     mbedtls_mpi_free(&D); mbedtls_mpi_free(&E); mbedtls_mpi_free(&DP);
     mbedtls_mpi_free(&DQ); mbedtls_mpi_free(&QP);