cassini-distro: Implement cassini distro features

The following cassini distro features are implemented:

* cassini-sdk
* security
* cassini-test

Neoverse N1 System Development Platform (N1SDP) reference board support
is addded.

Signed-off-by: Devaraj Ranganna <devaraj.ranganna@arm.com>
Signed-off-by: Kamil Dziezyk <kamil.dziezyk@arm.com>
Signed-off-by: Hugo L'Hostis <hugo.lhostis@arm.com>
Signed-off-by: Joel Goddard <joel.goddard@arm.com>
Signed-off-by: Richard Neill <richard.neill@arm.com>
Signed-off-by: Diego Sueiro <diego.sueiro@arm.com>
Signed-off-by: Nathan Dunne <Nathan.Dunne@arm.com>
Change-Id: Ib3452fc438ab78c57cbedf9bdf8ba6fd86ca0a21

Issue-Id: OSSEMBEDA-1723
Issue-Id: OSSEMBEDA-1630

Change-Id: I9bccb01ae73d760ac47629319e5e6befd8e76ec4