drm: bridge: dw-hdmi: Remove device type from platform data

The device type isn't used anymore now that workarounds and PHY-specific
operations are performed based on version information read at runtime.
Remove it.

Signed-off-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Tested-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Jose Abreu <joabreu@synopsys.com>
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20170303172007.26541-9-laurent.pinchart+renesas@ideasonboard.com