etnaviv: only flush resource to self if no scanout buffer exists

etnaviv: only flush resource to self if no scanout buffer exists

Currently a resource flush may trigger a self resolve, even if a scanout buffer
exists, but is up to date. If a scanout buffer exists we only ever want to
flush the resource to the scanout buffer. This fixes a performance regression.

Fixes: dda956340ce9 (etnaviv: resolve tile status when flushing resource)
Cc: mesa-stable@lists.freedesktop.org
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Christian Gmeiner <christian.gmeiner@gmail.com>