cmn_rhodes: prepare module for ccix support

This patch adds initial support for discovering the CCIX Gateway blocks
(CXG_RA, CXG_HA and CXLA registers) and configuring the RNSAM to target
a CCIX node. The required configuration structures to configure RNSAM
table has been added.

Change-Id: I580ad8d03297e82fe3819643d0b11ea8974c520a
Signed-off-by: Vijayenthiran Subramaniam <vijayenthiran.subramaniam@arm.com>