This patch replaces ->mode_fixup() with ->atomic_check() so that
a full modeset can be requested from there when crtc_state->active
is changed to be true(which implies only connector's DPMS is brought
out of "Off" status, though not necessarily).  Bridge functions are
added or changed to accommodate the ->atomic_check() callback.  That
full modeset is needed by the up-coming patch which gets MIPI DSI
controller and PHY ready in ->mode_set(), because it makes sure
->mode_set() and ->atomic_disable() are called in pairs.

Cc: Andrzej Hajda <a.hajda@samsung.com>
Cc: Neil Armstrong <narmstrong@baylibre.com>
Cc: Robert Foss <robert.foss@linaro.org>
Cc: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
Cc: Jonas Karlman <jonas@kwiboo.se>
Cc: Jernej Skrabec <jernej.skrabec@siol.net>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Guido Günther <agx@sigxcpu.org>
Cc: Robert Chiras <robert.chiras@nxp.com>
Cc: NXP Linux Team <linux-imx@nxp.com>
Signed-off-by: Liu Ying <victor.liu@nxp.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1619170003-4817-2-git-send-email-victor.liu@nxp.com