serial: imx: do not stop Rx/Tx on termios change

imx_set_termios(): stopping receiver and transmitter does harm when
something that doesn't touch transmission format/rate changes, such as
RTS/CTS handshake.

OTOH, it does no good on baud rate or format change, as
synchronization on upper-level protocols is still required to do it
right.

Therefore, just stop doing it.
Signed-off-by: Sergey Organov <sorganov@gmail.com>
Link: https://lore.kernel.org/r/1567017475-11919-3-git-send-email-sorganov@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/imx.c

@@ -1652,9 +1652,6 @@ imx_uart_set_termios(struct uart_port *port, struct ktermios *termios,
 			UCR1);
 	imx_uart_writel(sport, old_ucr2 & ~UCR2_ATEN, UCR2);
 
-	/* then, disable everything */
-	imx_uart_writel(sport, old_ucr2 & ~(UCR2_TXEN | UCR2_RXEN | UCR2_ATEN), UCR2);
-
 	/* custom-baudrate handling */
 	div = sport->port.uartclk / (baud * 16);
 	if (baud == 38400 && quot != div)