drm/bridge: ptn3460: Convert to I2C driver model

Use drm_bridge helpers to modify the driver to support I2C driver model.

Signed-off-by: Ajay Kumar <ajaykumar.rs@samsung.com>
Acked-by: Inki Dae <inki.dae@samsung.com>
Tested-by: Rahul Sharma <rahul.sharma@samsung.com>
Tested-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Tested-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Tested-by: Sjoerd Simons <sjoerd.simons@collabora.co.uk>
[treding@nvidia.com: remove recursive dependency on I2C]
Signed-off-by: Thierry Reding <treding@nvidia.com>