Bluetooth: Remove the device from the list in the destructor

The current code removes the device from the device list in several
places. Do it only in the destructor instead and in the error path of
rfcomm_add_dev() if the device couldn't be initialized.

Signed-off-by: Gianluca Anzolin <gianluca@sottospazio.it>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>