OMAPDSS: DISPC: reject interlace for lcd out

OMAP2/3 does not support interlace for LCD out. OMAP4+ does, but is not
supported by the driver at the moment.

The driver still accepts interlaced mode for LCD out, causing broken
display output.

This patch makes dispc reject interlace for LCD out.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>