OMAP: DSS2: add panel-dvi driver

We have currently panel-generic-dpi driver, which is a combined driver
for dummy panels and also for DVI output.

The aim is to split the panel-generic-dpi into two, one for fixed size
dummy panels connected via DPI, and the other (this) for variable
resolution output which supports DDC channel (in practice a DVI framer
chip connected to DPI output).

Original i2c code by: Ricardo Salveti de Araujo
<ricardo.salveti@canonical.com>

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