Fix double free in kernel driver probe clean up

If the probe function is past the NPU device registration when a failure
occurs, the device instance will be freed twice causing a crash. This
occurs because the device's release callback will free the device
instance when the device is unregistered and then the probe clean up
will attempt to free it again.

To resolve this, the probe will now only directly free the device
instance if the registration fails and otherwise let the device's
release callback handle it.

Change-Id: Iafe87e7ca44b91f8e0e2e870106a4b8c2a69dd8f
Signed-off-by: Mikael Olsson <mikael.olsson@arm.com>