docs: add binding for vm availability messages

SPs can subscribe to get notified when a VM is created or destroyed.
This patch adds a binding to the SP manifest to represent this.

Signed-off-by: Balint Dobszay <balint.dobszay@arm.com>
Change-Id: Ib23655575f471a22bcf261f70f2c4124a3f292c3
1 file changed