arm64: dts: sparx5: Add Sparx5 SoC DPLL clock

This adds a DPLL clock to the Sparx5 SoC. It is used to generate clock
to misc peripherals, specifically the SDHCI/eMMC controller.

Link: https://lore.kernel.org/r/20200615133242.24911-10-lars.povlsen@microchip.com


Signed-off-by: Lars Povlsen <lars.povlsen@microchip.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>