drm/omap: dsi: send nop instead of page & column

The OMAP DSI command mode panel driver used to send page & column
address before each frame update, and this code was moved into the DSI
host driver when converting it to the DRM bridge model.

However, it's not really required to send the page & column address
before each frame. It's also something that doesn't really belong to the
DSI host driver, so we should drop the code.

That said, frame updates break if we don't send _something_ between the
frames. A NOP command does the trick.

It is not clear if this behavior is as expected from a DSI command mode
frame transfer, or is it a feature/issue with OMAP DSI driver, or a
feature/issue in the command mode panel used.

Most likely this is related to the following from the DSI spec:

"To enable PHY synchronization the host processor should periodically
end HS transmission and drive the Data Lanes to the LP state. This
transition should take place at least once per frame."

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201215104657.802264-62-tomi.valkeinen@ti.com