drm: rcar-du: Support interlaced video output through vsp1

Use the newly exposed VSP1 interface to enable interlaced frame support
through the VSP1 LIF pipelines.

The DSMR register is updated to set the ODEV flag on interlaced
pipelines, thus defining an interlaced stream as having the ODD field
located in the second half (BOTTOM) of the frame buffer.

Signed-off-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>

 - Fix commit title
 - Document change to DSMR
 - Configure through vsp1_du_setup_lif(), rather than
2 files changed