Dualcpu: Align TF-M NS mailbox change

Implement tfm_ns_mailbox_os_spin_lock() and
tfm_ns_mailbox_os_spin_unlock().
Include tfm_ns_mailbox_test.h instead of tfm_ns_mailbox.h in multi-core
test.

Signed-off-by: David Hu <david.hu@arm.com>
Change-Id: Ibc29ce8d463cf13d6cbff4f6a51074fdb283ef1a
3 files changed