drm/bridge: add connector_init interface in drm_bridge_funcs

Add the connector_init callback so a bridge is allowed to
initialize the connector passed to itself. This is useful
in certain cases like, the connector and bridge are created
in two different modules, while the connector funcs need
access extra information of the bridge. This callback offers
the opportunity to override the connector's behavior.

CRs-Fixed: 2140653
Change-Id: Iee228dd610d2e72d0a9e0bd960b0715b4ea6c644
Signed-off-by: Ray Zhang <rayz@codeaurora.org>
Signed-off-by: Narendra Muppalla <NarendraM@codeaurora.org>