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.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>