drivers: clk: st: Remove stih415-416 clock support

STiH415 and STiH416 platforms are no longer used.
these platforms will be deprecated for the next kernel.

Signed-off-by: Gabriel Fernandez <gabriel.fernandez@st.com>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Peter Griffin <peter.griffin@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>