drivers: serial: fix console hang when waken up from PM3

The console can't input when waken up from PM3, as get the wrong
usart_intenset when process PM_DEVICE_ACTION_TURN_ON and the
USART interrupt is not enabled. Only saving usart_intenset after
PM action of PM_DEVICE_ACTION_TURN_OFF can fix this issue.

Signed-off-by: Maochen Wang <maochen.wang@nxp.com>

Author: MaochenWang1

drivers/serial/uart_mcux_flexcomm.c

@@ -1123,14 +1123,13 @@ static int mcux_flexcomm_pm_action(const struct device *dev, enum pm_device_acti
 	const struct mcux_flexcomm_config *config = dev->config;
 	int ret;
 
-	usart_intenset = USART_GetEnabledInterrupts(config->base);
-
 	switch (action) {
 	case PM_DEVICE_ACTION_RESUME:
 		break;
 	case PM_DEVICE_ACTION_SUSPEND:
 		break;
 	case PM_DEVICE_ACTION_TURN_OFF:
+		usart_intenset = USART_GetEnabledInterrupts(config->base);
 		break;
 	case PM_DEVICE_ACTION_TURN_ON:
 		ret = mcux_flexcomm_init_common(dev);