ieee802154: ca8210: prevent memory leak

In ca8210_probe the allocated pdata needs to be assigned to
spi_device->dev.platform_data before calling ca8210_get_platform_data.
Othrwise when ca8210_get_platform_data fails pdata cannot be released.

Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
Link: https://lore.kernel.org/r/20190917224713.26371-1-navid.emamdoost@gmail.com
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>
