unbind/bind w1-gpio with device tree produce a crash

[Ingo Flaschberger <ingo.flaschberger@gmail.com>]

If w1-gpio is probed via device-tree configuration, pdata is allocated 
via devm_kzalloc.
When the device is unbind (and bind later) the allocated memory of pdate 
is freed - but it will not be allocacted again.

static int w1_gpio_probe(struct platform_device *pdev)
         struct w1_bus_master *master;
         struct w1_gpio_platform_data *pdata = pdev->dev.platform_data;
         int err;

         if(pdata == NULL) {
                 if (of_have_populated_dt()) {
                         err = w1_gpio_probe_dt(pdev);
                         if (err < 0)
                                 return err;
                 }
         }

How to detect if pdata was allocated via device-tree devm_kzalloc and 
not "hardcoded"?
Then I could set pdev->dev.platform_data to NULL in w1_gpio_remove which 
will solve the crash.

Kind regards,
    Ingo Flascherger