etnaviv: add debug option to disable linear PE feature

etnaviv: add debug option to disable linear PE feature

Linear PE has already shown to have some rough corner cases in the hardware
and also has performance implications. Add a debug option to allow to disable
the feature, so users can more easily check if some issue is caused by this
feature.

CC: mesa-stable #22.2
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Guido Günther <agx@sigxcpu.org>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/18232>