drm: drop _mode_ from drm_mode_connector_attach_encoder

Again to align with the usual prefix of just drm_connector_. Again
done with sed + manual fixup for indent issues.

Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180709084016.23750-7-daniel.vetter@ffwll.ch