cmake: product/morello

This change adds CMake build support for morello platform

Please note that firmware targets do not use libRTX_CM3.a
or RTX_CM3.lib, instead in CMake build, the library
is built using sources.

Change-Id: Ic150e116af9e13474a128a61268859fdb50e1c18
Signed-off-by: Girish Pathak <girish.pathak@arm.com>