drm: bridge: dw-hdmi: Remove unused field from dw_hdmi_plat_data

The input_bus_format field of struct dw_hdmi_plat_data is unused. Remove
it.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200526011505.31884-14-laurent.pinchart+renesas@ideasonboard.com