When possible re-use the already allocated RX node for notifications.
Store (retain) RX node and Link element on RX if NTF could occur.
Pass link element to LLCP (ull_cp_rx()) together with RX node.
New RX node type RETAIN introduced to signal retention
When no RX node is available allocate one and hold off TX on procedures
until such time that a node is available for NTF.
In case waiting for NTF buffer avail is needed, allocate and store TX
node to use for TX once NTF becomes available.
CIS Established (incl. timeout handling) is now handled entirely as a
specific event driven by ull_conn_iso - ie removal of procedure check
of cis->established and cis->expire, as this is doubling mechanism
in the conn_iso context.
Unit test and helpers updated to handle new node type.
Function ull_cp_release_ntf() was used only in unit test, so moved to
helper context.
Updating release_ntf to handle the fact that with piggy-backing in test
context the node used for NTF can be from two different memory pools
Signed-off-by: Erik Brockhoff <erbr@oticon.com>
998512f59b