drm/bridge: analogix_dp: Support to get &analogix_dp_device.plat_data and &analogix_dp_device.aux

Add two new functions: one to find &analogix_dp_device.plat_data via
&drm_dp_aux, and the other to get &analogix_dp_device.aux. Both of them
serve for the function of getting panel from DP AUX bus, which is why
they are included in a single commit.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Damon Ding <damon.ding@rock-chips.com>
Link: https://lore.kernel.org/r/20250310104114.2608063-6-damon.ding@rock-chips.com


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>