dm: gpio: vybrid_gpio: Correct driver's use of bind() method

It does not look like this driver needs to use a bind() method. It does
not manually create devices with device_bind() nor does it create devices
using U_BOOT_DEVICE(). It seems to only use device tree.

Therefore the manual allocation of platform data is not needed and is
confusing. Also platform data should be set up by the ofdata_to_platdata()
method, not bind().

Update the driver in case others use it as a model in future.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reported-by: Adam Ford <aford173@gmail.com>