clock: milbeaut: Add Milbeaut M10V clock controller

The M10V of the Milbeaut SoCs has an on-chip controller that derive
mostly clocks from a single external clock, using PLLs, dividers,
multiplexers and gates. Since the PLLs have already been started and
will not stop / restart, they are fixed factor. The gates will be added
in later patch (all of the gates are off state now).

Signed-off-by: Sugaya Taichi <sugaya.taichi@socionext.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>