Dualcpu: Adjust the definition number of mailbox queue slots

If multiple outstanding NS PSA Client calls feature is enabled,
require platform to define NUM_MAILBOX_QUEUE_SLOT in platform
specific device_cfg.h.
Otherwise, define NUM_MAILBOX_QUEUE_SLOT as 1 in tfm_mailbox.h.

Also fix the initialization of queue empty slot status variables
since NUM_MAILBOX_QUEUE_SLOT can be set to 32.

Change-Id: I26ea1283f8c6cad9ebe31b24c06ddccf3d2e5699
Signed-off-by: David Hu <david.hu@arm.com>
3 files changed