drm/msm/dp: use correct lifetime device for devm_drm_bridge_add

The lifetime of the created drm_bridge is attached to the drm_device
rather than the DP's platform_device. Use correct lifetime for
devm_drm_bridge_add() call.

Fixes: 61a72d5e ("drm/msm/dp: switch to devm_drm_bridge_add()")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/562203/
Link: https://lore.kernel.org/r/20231011214705.375738-4-dmitry.baryshkov@linaro.org