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

The struct resource is not used for anything else, so we can simplify
the code a bit by using the helper function.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20220615045543.62813-3-samuel@sholland.org