Bluetooth: L2CAP: Fix regressions caused by reusing ident

Bluetooth: L2CAP: Fix regressions caused by reusing ident

This attempt to fix regressions caused by reusing ident which apparently
is not handled well on certain stacks causing the stack to not respond to
requests, so instead of simple returning the first unallocated id this
stores the last used tx_ident and then attempt to use the next until all
available ids are exausted and then cycle starting over to 1.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=221120
Link: https://bugzilla.kernel.org/show_bug.cgi?id=221177
Fixes: 6c3ea155e5ee ("Bluetooth: L2CAP: Fix not tracking outstanding TX ident")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Tested-by: Christian Eggers <ceggers@arri.de>