drm/msm/dp: fix aux-bus EP lifetime

drm/msm/dp: fix aux-bus EP lifetime

Device-managed resources allocated post component bind must be tied to
the lifetime of the aggregate DRM device or they will not necessarily be
released when binding of the aggregate device is deferred.

This can lead resource leaks or failure to bind the aggregate device
when binding is later retried and a second attempt to allocate the
resources is made.

For the DP aux-bus, an attempt to populate the bus a second time will
simply fail ("DP AUX EP device already populated").

Fix this by tying the lifetime of the EP device to the DRM device rather
than DP controller platform device.

Fixes: c3bf8e21b38a ("drm/msm/dp: Add eDP support via aux_bus")
Cc: stable@vger.kernel.org      # 5.19
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Tested-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
Reviewed-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/502672/
Link: https://lore.kernel.org/r/20220913085320.8577-7-johan+linaro@kernel.org
Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>