[nrf fromtree] tests: drivers: Trigger drop event for proper clean-up

Add I2S_TRIGGER_DROP call in the error test to ensure proper cleanup
after stopping the I2S device. This validates that the drop trigger
is properly handled in error conditions and resources are released.

Signed-off-by: Erdem Simsek <erdem.simsek@nordicsemi.no>
(cherry picked from commit aec9da0)

Author: Erdem Simsek

tests/drivers/i2s/i2s_api/src/test_i2s_errors.c

@@ -76,6 +76,9 @@ ZTEST_USER(i2s_errors, test_i2s_config_attempt_in_wrong_state)
 	err = i2s_trigger(dev_i2s, I2S_DIR_TX, I2S_TRIGGER_STOP);
 	zassert_equal(err, 0, "I2S_TRIGGER_STOP unexpected error: %d", err);
 
+	err = i2s_trigger(dev_i2s, I2S_DIR_TX, I2S_TRIGGER_DROP);
+	zassert_equal(err, 0, "I2S_TRIGGER_DROP unexpected error: %d", err);
+
 	zassert_not_equal(
 		config_err, 0,
 		"I2S configuration should not be possible in states other than I2S_STATE_READY");