[nrf fromlist] tests: boards: nrf: i2c_slave: fix incorrect error code

Errno codes are returned now.

Upstream PR #: 98569

Signed-off-by: Nikodem Kastelik <nikodem.kastelik@nordicsemi.no>

Author: nika-nordic

tests/boards/nrf/i2c/i2c_slave/src/main.c

@@ -80,7 +80,7 @@ static void *test_setup(void)
 	};
 	int ret;
 
-	zassert_equal(NRFX_SUCCESS, nrfx_twis_init(&twis, &config, i2s_slave_handler),
+	zassert_equal(0, nrfx_twis_init(&twis, &config, i2s_slave_handler),
 		      "TWIS initialization failed");
 
 	PINCTRL_DT_DEFINE(NODE_TWIS);