tty: serial: Fix mediatek UART driver setting baudrate issue

In mtk8250_set_termios function, calculating quot value can not be zero,
otherwise, using DIV_ROUND_CLOSEST(port->uartclk, quot * baud) will fail due to
divisor is zero.
Signed-off-by: Eddie Huang <eddie.huang@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_mtk.c

@@ -74,14 +74,14 @@ mtk8250_set_termios(struct uart_port *port, struct ktermios *termios,
 		/* Set to next lower baudrate supported */
 		if ((baud == 500000) || (baud == 576000))
 			baud = 460800;
-		quot = DIV_ROUND_CLOSEST(port->uartclk, 4 * baud);
+		quot = DIV_ROUND_UP(port->uartclk, 4 * baud);
 	} else {
 		serial_port_out(port, UART_MTK_HIGHS, 0x3);
 
 		/* Set to highest baudrate supported */
 		if (baud >= 1152000)
 			baud = 921600;
-		quot = DIV_ROUND_CLOSEST(port->uartclk, 256 * baud);
+		quot = DIV_ROUND_UP(port->uartclk, 256 * baud);
 	}
 
 	/*