imx-drm: parallel-display: honor 'native-mode' property when selecting video mode...

imx-drm: parallel-display: honor 'native-mode' property when selecting video mode from DT

This patch allows to select a specific video mode from a list of modes
defined in DT by setting the 'native-mode' property appropriately.

Since all current users of this driver have only one mode defined in
their .dts files, the patch does not change the behaviour of this
driver on the affected platforms.

Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
Reviewed-by: Marek Vasut <marex@denx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>