ARM: omap2plus_defconfig: Enable some display features

Now that we have panel support for DT based booting,
let's make it usable and enable most things as modules.

Note that omap3 boards need also the ads7847 module for
the panel that we're now changing to a loadable module.
And n900 seems to require setting the brightness via
sysfs for acx565akm/brightness after modprobe of
panel_sony_acx565akm and omapfb.

Signed-off-by: Tony Lindgren <tony@atomide.com>