clk: sparx5: Add Sparx5 SoC DPLL clock driver

This adds a device driver for the Sparx5 SoC DPLL clock

Signed-off-by: Lars Povlsen <lars.povlsen@microchip.com>
Link: https://lore.kernel.org/r/20200727084211.6632-9-lars.povlsen@microchip.com
Signed-off-by: Stephen Boyd <sboyd@kernel.org>