fdts: n1sdp: DTS file for single-chip and multi-chip environment. ...

N1SDP supports both single-chip and multi-chip environment.
Added  DTS file for both type of environment.
Enabled DTS files compilation for N1SDP platform.

Change-Id: I66af88dcfb841893eb6ed2ca18d3025de81236a0
Co-authored-by: Robin Murphy <Robin.Murphy@arm.com>
Co-authored-by: Sayanta Pattanayak <sayanta.pattanayak@arm.com>
Co-authored-by: Manoj Kumar <manoj.kumar3@arm.com>
Co-authored-by: Anurag Koul <anurag.koul@arm.com>
Signed-off-by: Sayanta Pattanayak <sayanta.pattanayak@arm.com>