Bluetooth: Set disc_timeout to 0 when calling hci_chan_del

The hci_chan_del() function is used in scenarios where we've decided we
want to get rid of the underlying baseband link. It makes therefore
sense to force the disc_timeout to 0 so that the disconnection routines
are immediately scheduled.

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