sunxi: video: Rename tve.c to tve_common.c

In order to avoid future confusion with similary named files, rename
tve.c to tve_common.c. New name better represents the fact that this file
holds code which can be and will be shared between multiple drivers.

Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Reviewed-by: Simon Glass <sjg@chromium.org>