Build: Introduce TFM_CONFIG_USE_TRUSTZONE

Both CMake variable and C define.
Default to ON, set to OFF in appropriate platform configs.
Used to control inclusion of veneers, etc.

Change-Id: Ic1abb17fc6c5b8ac23b5dff09b52aef4946b6f94
Signed-off-by: Chris Brand <chris.brand@cypress.com>
22 files changed