- Introduce new file `corstone1000-extsys.inc` to define variables related
to the external system.
- Ensure this file is included only when MACHINE_FEATURES do contain
corstone1000-extsys.
This change makes external system configuration modular and only applied
when explicitly enabled through machine features.
Signed-off-by: Michael Safwat <michael.safwat@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>