arm64: allwinner: h5: add compatible string for DE2 CCU

The DE2 CCU on Allwinner H5 SoC has a slightly different behavior than
the one on H3, so the compatible string is not set in the common DTSI
file.

Add the compatible string of H5 DE2 CCU in H5 DTSI file.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Chen-Yu Tsai <wens@csie.org>