drm: bridge: dw-hdmi: Remove encoder field from struct dw_hdmi

The field isn't needed, remove it.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Jose Abreu <joabreu@synopsys.com>
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20170117082910.27023-6-laurent.pinchart+renesas@ideasonboard.com