drm/etnaviv: disable MLCG and pulse eater on GPU reset

Module level clock gating and the pulse eater might interfere with
the GPU reset, as they both have the potential to stop the clock
and thus reset propagation to parts of the GPU.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Christian Gmeiner <cgmeiner@igalia.com>