Bluetooth: Remove unnecessary work structs from SMP code

When the SMP code was initially created (mid-2011) parts of the
Bluetooth subsystem were still not converted to use workqueues. This
meant that the crypto calls, which could sleep, couldn't be called
directly. Because of this the "confirm" and "random" work structs were
introduced.

These days the entire Bluetooth subsystem runs through workqueues which
makes these structs unnecessary. This patch removes them and converts
the calls to queue them to use direct function calls instead.

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