Revert "drm/bridge: Rename bridge helpers targeting a bridge chain"

This reverts commit bb08be72.

It breaks the Android kernel api and was added only because of a tiny
drm driver bugfix for an issue that can not ever really be hit, so it is
safe to revert.

Bug: 161946584
Change-Id: I048f2ee1cfd60416b408af65b403286e282efcdd
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>