doc: Update the cot-binding for nv-counter node

Updated the cot-binding documentation to add 'id'
property for the trusted and non-trusted nv-counters.

Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
Change-Id: If1c628c5b90fe403dd96c7cd0cd04f37288c965c
1 file changed