drm/etnaviv: drop driver owner assignment

Core in platform_driver_register() already sets the .owner, so driver
does not need to.  Whatever is set here will be anyway overwritten by
main driver calling platform_driver_register().

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Christian Gmeiner <cgmeiner@igalia.com>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>