drm/bridge: properly refcount DT nodes in aux bridge drivers

The aux-bridge and aux-hpd-bridge drivers didn't call of_node_get() on
the device nodes further used for dev->of_node and platform data. When
bridge devices are released, the reference counts are decreased,
resulting in refcount underflow / use-after-free warnings. Get
corresponding refcounts during AUX bridge allocation.

Reported-by: Luca Weiss <luca.weiss@fairphone.com>
Fixes: 2a047391 ("drm/bridge: add transparent bridge helper")
Fixes: 26f4bac3

 ("drm/bridge: aux-hpd: Replace of_device.h with explicit include")
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20231216235910.911958-1-dmitry.baryshkov@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>