Drop the "if (!dev->platform_data)" check, this seems to be an attempt
for allowing loading the driver on devices without devicetree stemming
from the initial commit of the driver (with the presumed intention being
the "return -ENODEV" else branch getting replaced with something else).

With the new "linux,skip-init" and "linux,read-back-settings" properties
the driver can actually supports devices without devicetree and this
check no longer makes sense.

While at it, also switch to dev_err_probe(), which is already used in
various other places in the driver.
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>