drm/bridge: analogix_dp: passing the connector as an argument in .get_modes()

It's better to pass the connector to platform driver in .get_modes()
callback, just like what the .get_modes() helper function designed.

Signed-off-by: Yakir Yang <ykk@rock-chips.com>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Tomasz Figa <tomasz.figa@chromium.com>