drm/etnaviv: add missing quirks for GC300

The GC300's features register doesn't specify that a 2D pipe is
available, and like the GC600, its idle register reports zero bits where
modules aren't present.

Signed-off-by: Doug Brown <doug@schmorgal.com>
Reviewed-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>