drm/etnaviv: Replace the '&pdev->dev' with 'dev'

In the etnaviv_pdev_probe() and etnaviv_gpu_platform_probe() function, the
value of '&pdev->dev' has been cached to the local auto variable 'dev'.
But some callers use 'dev', while the rest use '&pdev->dev'. To keep it
consistent, use 'dev' uniformly.

Tested-by: Christian Gmeiner <cgmeiner@igalia.com>
Signed-off-by: Sui Jingfeng <sui.jingfeng@linux.dev>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>