platform/x86: barco-p50-gpio: Add check for platform_driver_register

As platform_driver_register() could fail, it should be better
to deal with the return value in order to maintain the code
consisitency.

Fixes: 86af1d02

 ("platform/x86: Support for EC-connected GPIOs for identify LED/button on Barco P50 board")
Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
Acked-by: Peter Korsgaard <peter.korsgaard@barco.com>
Link: https://lore.kernel.org/r/20220526090345.1444172-1-jiasheng@iscas.ac.cn
Signed-off-by: Hans de Goede <hdegoede@redhat.com>