Bluetooth: Store parameter length with pending mgmt commands

As preparation for making generic cmd_complete responses possible we'll
need to track the parameter length in addition to just a pointer to
them. This patch adds the necessary variable to the pending_cmd struct.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

diff --cc net/bluetooth/mgmt.c
Simple merge