Bluetooth: Reset the security timer when a command is queued

Each time a SMP command is enqueued, we reset the SMP timer,
this way we follow exactly what the spec mandates:

"The Security Manager Timer shall be reset when an L2CAP SMP command is
queued for transmission." Vol. 3, Part H, Section 3.4

Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@openbossa.org>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>