drm/etnaviv: add flushing logic for MMUv2

Flushing works differently on MMUv2, in that it's only necessary
to set a single bit in the control register to flush all translation
units. A semaphore stall then makes sure that the flush has propagated
properly.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
1 file changed