drivers: clk: adi: Add in SC5XX-family clock driver

This adds support for the SC5XX clock trees which are required for reading
clock speeds on the SoCs. This is largely a port of the same support for
Linux, which has not yet been submitted upstream.

Co-developed-by: Greg Malysa <greg.malysa@timesys.com>
Signed-off-by: Greg Malysa <greg.malysa@timesys.com>
Co-developed-by: Ian Roberts <ian.roberts@timesys.com>
Signed-off-by: Ian Roberts <ian.roberts@timesys.com>
Signed-off-by: Vasileios Bimpikas <vasileios.bimpikas@analog.com>
Signed-off-by: Utsav Agarwal <utsav.agarwal@analog.com>
Signed-off-by: Arturs Artamonovs <arturs.artamonovs@analog.com>
Signed-off-by: Nathan Barrett-Morrison <nathan.morrison@timesys.com>