juno: Add SoC clock support for RAM

This patch adds the SoC clock support for Juno board and
the management of the cluster clocks.

Change-Id: Ice954f4628d0c2535586f469efac84d42957e711
Co-authored-by: Ronald Cron <Ronald.Cron@arm.com>
Signed-off-by: Elieva Pignat <Elieva.Pignat@arm.com>
Signed-off-by: Jim Quigley <jim.quigley@arm.com>
Signed-off-by: Raphael Gault <raphael.gault@arm.com>