Bluetooth: Controller: Introduce rate-limiting on stack analysis

In case the controller is receiving PDUs very rapidly, prevent it from
spamming the logs by limiting its stack analysis to at most once every
5 seconds.

Change-Id: I31c70d28e8af62b27172a4a77bf6e614ea3e20eb
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>