N1SDP supports multichip configuration wherein n1sdp boards are
connected over high speed coherent CCIX link, for now only dual-chip
is supported.

Whether or not multiple chips are present is dynamically probed by
SCP firmware and passed on to TF-A, routing table will be set up
only if multiple chips are present.

Initialize GIC-600 multichip operation by overriding the default GICR
frames with array of GICR frames and setting the chip 0 as routing
table owner.

Change-Id: Ida35672be4bbf4c517469a5b330548d75e593ff2
Signed-off-by: Manish Pandey <manish.pandey2@arm.com>