drm/etnaviv: add total hi bandwidth perfcounter

These two perf counters represent the total read and write
GPU bandwidth in terms of 64bits.

The used sequence was taken from Vivante kernel driver.

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>