etnaviv: native fence fd support

etnaviv: native fence fd support

This adds native fence fd support to etnaviv, similarly to commit
0b98e84e9ba0 ("freedreno: native fence fd"), enabled for kernel
driver version 1.1 or later.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-By: Wladimir J. van der Laan <laanwj@gmail.com>
Reviewed-by: Christian Gmeiner <christian.gmeiner@gmail.com>