net: sun8i_emac: Fix build for non-H3/H5 SoCs

Only the H3/H5 SoCs have an internal PHY and its related clock and
reset controls.

Use an #ifdef to guard the internal PHY control code block so it
can be built for other SoCs, such as the A83T or A64.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Reviewed-by: Joe Hershberger <joe.hershberger@ni.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>