tty/serial: atmel: fix TX path in atmel_console_write()

A side effect of 89d8232411a8 ("tty/serial: atmel_serial: BUG: stop DMA
from transmitting in stop_tx") is that the console can be called with
TX path disabled. Then the system would hang trying to push charecters
out in atmel_console_putchar().

Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Fixes: 89d8232411a8 ("tty/serial: atmel_serial: BUG: stop DMA from transmitting
in stop_tx")
Cc: stable <stable@vger.kernel.org>	#4.4+
Acked-by: Richard Genoud <richard.genoud@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/atmel_serial.c

@@ -2488,6 +2488,9 @@ static void atmel_console_write(struct console *co, const char *s, u_int count)
 	pdc_tx = atmel_uart_readl(port, ATMEL_PDC_PTSR) & ATMEL_PDC_TXTEN;
 	atmel_uart_writel(port, ATMEL_PDC_PTCR, ATMEL_PDC_TXTDIS);
 
+	/* Make sure that tx path is actually able to send characters */
+	atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXEN);
+
 	uart_console_write(port, s, count, atmel_console_putchar);
 
 	/*