drm/bridge/synopsys: dw-hdmi: Use bridge->mode_valid() callback

Now that we have a callback to check if bridge supports a given mode
we can use it in Synopsys Designware HDMI bridge so that we restrict
the number of probbed modes to the ones we can actually display.

Also, there is no need to use mode_fixup() callback as mode_valid()
will handle the mode validation.

NOTE: I also had to change the pdata declaration of mode_valid
custom callback so that the passed modes are const. I also changed
in the platforms I found. Not even compiled it though.

Signed-off-by: Jose Abreu <joabreu@synopsys.com>
Acked-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Carlos Palminha <palminha@synopsys.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Archit Taneja <architt@codeaurora.org>
Cc: Andrzej Hajda <a.hajda@samsung.com>
Cc: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Carlo Caione <carlo@caione.org>
Cc: Kevin Hilman <khilman@baylibre.com>
Cc: Mark Yao <mark.yao@rock-chips.com>
Cc: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Link: http://patchwork.freedesktop.org/patch/msgid/3d8d449e4d13d2535fa292c75f5fa931de4a4fa8.1495720737.git.joabreu@synopsys.com