ARM: dts: remove stih415-clks.h

Since v4.8, STiH415/416 clock support has
been removed [1], these platform doesn't boot.
We can remove DTS files related to these socs.

[1] https://patchwork.kernel.org/patch/9157571/



Signed-off-by: Patrice Chotard <patrice.chotard@st.com>