drm/tilcdc: support pixel widths greater than 1024

TI LCD controller version 2 has an extended eleventh
bit that enables horizontal resolutions greater than
1024 pixels to be specified (upto 2048).  This patch
adds support for setting this bit on LCDC V2.

Signed-off-by: Darren Etheridge <detheridge@ti.com>
Acked-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>