The DE2 in H3/H5 has a clock control unit in it, and the behavior is
slightly different between H3 and H5.

Add the common parts in H3/H5 DTSI, and add the compatible string in H3
DTSI.

The compatible string of H5 DE2 CCU will be added in a separated patch.
Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Chen-Yu Tsai <wens@csie.org>