ptp: create "pins" together with the rest of attributes

ptp: create "pins" together with the rest of attributes

commit 85a66e55019583da1e0f18706b7a8281c9f6de5b upstream.

Let's switch to using device_create_with_groups(), which will allow us to
create "pins" attribute group together with the rest of ptp device
attributes, and before userspace gets notified about ptp device creation.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>