drm/etnaviv: remove owner assignment from platform_driver

This platform_driver does not need to set an owner as it will be
populated by the driver core.

Generated by scripts/coccinelle/api/platform_no_drv_owner.cocci.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>