Bluetooth: Refactor mgmt_pending_foreach

This patch does a trivial refactor in mgmt_pending_foreach function.
It replaces list_for_each_safe by list_for_each_entry_safe, simplifying
the function.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>