staging: olpc_dcon: drop XO-1.5 support for now

The vx855 stuff isn't upstream yet; for now, drop support for XO-1.5.
This will come back once the 1.5 code is in place (and will be in a form
that allows both 1.0 and 1.5 support to be compiled in at the same time),
but for now just remove it.  This is necessary to get the driver building.

Signed-off-by: Andres Salomon <dilinger@queued.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>