drm/etnaviv: stop getting the excl fence separately here

Just grab all fences in one go.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20211028132630.2330-3-christian.koenig@amd.com