serial: exar: Leave MPIOs as output for Commtech adapters

Commtech adapters apparently need the original setting as outputs, see
https://marc.info/?l=linux-gpio&m=149557425201323&w=2

. Account for that.

Fixes: 7dea8165 ("serial: exar: Preconfigure xr17v35x MPIOs as output")
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>