Many drm connectors do not need mode validation.
The patch makes this callback optional and removes dumb implementations.

v2: Rebase:
- imx move to a shared (but still dummy) ->mode_valid implementation.
- probe helpers have been extracted to drm_probe_helper.c

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com> (v1)
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

This patch exports ptn3460_init function so that other modules
can call this function.
Signed-off-by: NInki Dae <inki.dae@samsung.com>
Signed-off-by: NKyungmin Park <kyungmin.park@samsung.com>

This patch adds a drm_bridge driver for the PTN3460 DisplayPort to LVDS
bridge chip.
Signed-off-by: NSean Paul <seanpaul@chromium.org>
Signed-off-by: NInki Dae <inki.dae@samsung.com>