This fixes reloading of the GPIO driver for the same platform device
instance as created by the exar UART driver: First of all, the driver
sets drvdata to its own value during probing and does not restore the
original value on exit. But this won't help anyway as the core clears
drvdata after the driver left.

Set the platform device parent instead.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>