These settings used to be specified per-mode. But the device tree
bindings have these two values attached to the display and not to each
mode. Also for the supported boards it doesn't matter as they all only
have a single mode.

This is preparatory work to add devicetree support for the imxfb driver.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>