parisc: drivers: switch to dynamic root device

parisc: drivers: switch to dynamic root device

Driver core expects devices to be dynamically allocated and will, for
example, complain loudly if a device that lacks a release function
is ever freed.

Use root_device_register() to allocate and register the root device
instead of open coding using a static device.

While at it, drop the redundant additional reference taken at init.

Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Helge Deller <deller@gmx.de>