drm/sun4i: sun8i-hdmi-phy: Use of_device_get_match_data

Now that the HDMI PHY is using a platform driver, we can use the usual
helper function for getting the variant structure.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20220615045543.62813-2-samuel@sholland.org