Interface: Remove NS RTOS specific implementation

Move NS RTOS related interface code to tf-m-test to decouple TF-M from
NS specific implementation.
The removed code includes OS wrapper headers and RTOS specific
implementation.

Export tfm_ns_interface_dispatch() to NS as API to integrate with TF-M
NS interface.
Add an example of tfm_ns_interface_dispatch() implementation.

Change-Id: I9b331c32ac26551bfdbc4996eecd08efc7d7c2c3
Signed-off-by: David Hu <david.hu@arm.com>
13 files changed