drm/bridge: Add stubs for devm_drm_of_get_bridge when OF is disabled

drm/bridge: Add stubs for devm_drm_of_get_bridge when OF is disabled

If CONFIG_OF is disabled, devm_drm_of_get_bridge won't be compiled in
and drivers using that function will fail to build.

Add an inline stub so that we can still build-test those cases.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Link: https://patchwork.freedesktop.org/patch/msgid/20210928181333.1176840-1-maxime@cerno.tech