etnaviv: fix wrong surface TS clear size

etnaviv: fix wrong surface TS clear size

Clearing ts_size - ts_offset bytes in a level means we are clearing the
TS region of all layers in the level starting from the surface layer, so
clearing one surface might corrupt all other layers of a resource level.
Use the correct size to clear only the requested TS region.

Cc: mesa-stable
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>