tty: 8250: jz4780: Add MCR register bits for flow control.

These bits are not standard 550 uart.
For the serial module in the JZ4780, they need to be enabled
for flow control to work.

Found using old ingenic history to get BT to work on 3.16

Signed-off-by: Zubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>

drivers/tty/serial/8250/8250_core.c

@@ -48,6 +48,11 @@
 
 #include "8250.h"
 
+#ifdef CONFIG_MACH_JZ4780
+#define JZ_UART_MCR_MDCE		0x80 /* Enable modem function */
+#define JZ_UART_MCR_FCM		0x40 /* flow control by hardware */
+#endif
+
 /*
  * Configuration:
  *   share_irqs - whether we pass IRQF_SHARED to request_irq().  This option
@@ -1945,6 +1950,13 @@ static void serial8250_set_mctrl(struct uart_port *port, unsigned int mctrl)
 	if (mctrl & TIOCM_LOOP)
 		mcr |= UART_MCR_LOOP;
 
+	if (port->type == PORT_INGENIC_JZ4780) {
+		if (mctrl & JZ_UART_MCR_MDCE)
+			mcr |= JZ_UART_MCR_MDCE;
+		if (mctrl & JZ_UART_MCR_FCM)
+			mcr |= JZ_UART_MCR_FCM;
+	}
+
 	mcr = (mcr & up->mcr_mask) | up->mcr_force | up->mcr;
 
 	serial_port_out(port, UART_MCR, mcr);
@@ -2527,8 +2539,11 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
 	 */
 	up->ier &= ~UART_IER_MSI;
 	if (!(up->bugs & UART_BUG_NOMSR) &&
-			UART_ENABLE_MS(&up->port, termios->c_cflag))
+			UART_ENABLE_MS(&up->port, termios->c_cflag)) {
 		up->ier |= UART_IER_MSI;
+		if (port->type == PORT_INGENIC_JZ4780)
+			up->port.mctrl = JZ_UART_MCR_MDCE | JZ_UART_MCR_FCM;
+	}
 	if (up->capabilities & UART_CAP_UUE)
 		up->ier |= UART_IER_UUE;
 	if (up->capabilities & UART_CAP_RTOIE)