drm/bridge: anx7625: switch to devm_drm_of_get_bridge

The function "drm_of_find_panel_or_bridge" has been deprecated in
favor of "devm_drm_of_get_bridge".

Switch to the new function and reduce boilerplate.

Signed-off-by: José Expósito <jose.exposito89@gmail.com>
Reviewed-by: Maxime Ripard <maxime@cerno.tech>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220221072835.10032-1-jose.exposito89@gmail.com