Bluetooth: Add mgmt events for blacklisting

Add management interface events for blocking/unblocking a device.
Sender of the block device command gets cmd complete and other
mgmt sockets get the event. Event is also sent to mgmt sockets when
blocking is done with ioctl, e.g when blocking a device with
hciconfig. This makes it possible for bluetoothd to track status
of blocked devices when a third party block or unblocks a device.

Event sending is handled in mgmt_device_blocked function which gets
called from hci_blacklist_add in hci_core.c. A pending command is
added in mgmt_block_device, so that it can found when sending the
event - the event is not sent to the socket from which the pending
command came. Locks were moved out from hci_core.c to hci_sock.c
and mgmt.c, because locking is needed also for mgmt_pending_add in
mgmt.c.

Signed-off-by: Antti Julku <antti.julku@nokia.com>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>