serial: sc16is7xx: Read modem line state at startup

This patch sets the driver modem line state to the actual line state
at driver startup.

See: #5501

Signed-off-by: Earl Schmidt <[email protected]>
Signed-off-by: Phil Elwell <[email protected]>

Author: pelwell

drivers/tty/serial/sc16is7xx.c

@@ -1222,6 +1222,9 @@ static int sc16is7xx_startup(struct uart_port *port)
 	      SC16IS7XX_IER_MSI_BIT;
 	sc16is7xx_port_write(port, SC16IS7XX_IER_REG, val);
 
+	/* Initialize the Modem Control signals to current status */
+	one->old_mctrl = sc16is7xx_get_hwmctrl(port);
+
 	/* Enable modem status polling */
 	uart_port_lock_irqsave(port, &flags);
 	sc16is7xx_enable_ms(port);