video: fix composite video connector compatible string

The quite-recently-added analog-tv-connector bindings say that the
compatible string for composite video connector is
"composite-connector". That string is also used in the omap3-n900.dts
file. However, the connector driver uses "composite-video-connector", so
this has never worked.

While changing the driver's compatible string to "composite-connector"
would be safer, as published DT bindings should not be changed, I'd
rather fix the bindings in this case for two reasons:

* composite-connector is a bit too generic name, as it doesn't even hint
  at video.
* it's clear that this has never worked, which means no one has used
  those bindings, which should make it safe to change this.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>