serial_pl011: Set RTS during initialization

If the pl011 is connected to another device which has hardware
flow-control on, characters are never received by the pl011.
Asserting RTS when flow-control is off will have no effect.

This is in line with how Linux behaves.
Signed-off-by: NJoshua Housh <joshua.housh@calxeda.com>
Tested-by: NMarek Vasut <marex@denx.de>

drivers/serial/serial_pl01x.c

@@ -163,8 +163,8 @@ static int pl01x_serial_init(void)
 	}
 #endif
 	/* Finally, enable the UART */
-	writel(UART_PL011_CR_UARTEN | UART_PL011_CR_TXE | UART_PL011_CR_RXE,
-	       &regs->pl011_cr);
+	writel(UART_PL011_CR_UARTEN | UART_PL011_CR_TXE | UART_PL011_CR_RXE |
+	       UART_PL011_CR_RTS, &regs->pl011_cr);
 
 	return 0;
 }