drm/bridge: Move the struct drm_bridge member kerneldoc inline.

This makes it more likely that the docs stay updated with the code.

Signed-off-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20180606190431.1833-1-eric@anholt.net


Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>