etnaviv: remove copy of resource level in etna_surface

etnaviv: remove copy of resource level in etna_surface

Keeping a full copy of the resource level around in the surface is
confusing and this confusion has caused real bugs already. Get rid
of the copy by retrieving most of the information directly from the
etna_resource_level pointed at from the surface. Only the precomputed
offsets into the target and TS BOs need to be kept in the surface.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19814>