drivers: uart: Fix build error for lpuart without modem support

LPUART without modem support is used in some NXP socs. Build error
occurs for such socs because of accessing unavailable register.
Fix it by adding #if directive for checking modem support availability.

Signed-off-by: Michal Smola <[email protected]>

Author: michal-smola

drivers/serial/uart_mcux_lpuart.c

@@ -1092,13 +1092,17 @@ static int mcux_lpuart_configure_init(const struct device *dev, const struct uar
 
 	LPUART_Init(config->base, &uart_config, clock_freq);
 
+#if defined(FSL_FEATURE_LPUART_HAS_MODEM_SUPPORT) && \
+	FSL_FEATURE_LPUART_HAS_MODEM_SUPPORT
 	if (cfg->flow_ctrl == UART_CFG_FLOW_CTRL_RS485) {
 		/* Set the LPUART into RS485 mode (tx driver enable using RTS) */
 		config->base->MODIR |= LPUART_MODIR_TXRTSE(true);
 		if (!config->rs485_de_active_low) {
 			config->base->MODIR |= LPUART_MODIR_TXRTSPOL(1);
 		}
 	}
+#endif
+
 	/* Now can enable tx */
 	config->base->CTRL |= LPUART_CTRL_TE(true);