drm/etnaviv: rework perfmon query infrastructure

Report the correct perfmon domains and signals depending
on the supported feature flags.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: 9e2c2e27

 ("drm/etnaviv: add infrastructure to query perf counter")
Cc: stable@vger.kernel.org
Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>