clk: clk_meson: Add mux and div support for reparent and rate setting

clk: clk_meson: Add mux and div support for reparent and rate setting

This patch adds support for :
- Rate calculation through muxes and generic dividers
- Basic gate setting propagation
- Reparenting for muxes
- Clock rate setting through generic dividers without reparenting

Support is only added to the Composite VPU and VAPB clocks in order
to support the Video Processing Unit Power Domain clock setup.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>