serial: mxs-auart: Fix typo in sanity check

Detected by cppcheck:
[others/linux/drivers/tty/serial/mxs-auart.c:553]: (style) Same expression on both sides of '||'.

Signed-off-by: Thomas Jarosch <thomas.jarosch@intra2net.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>