Bluetooth: MGMT: Fix marking SCAN_RSP as not connectable

When receiving a scan response there is no way to know if the remote
device is connectable or not, so when it cannot be merged don't
make any assumption and instead just mark it with a new flag defined as
MGMT_DEV_FOUND_SCAN_RSP so userspace can tell it is a standalone
SCAN_RSP.

Link: https://lore.kernel.org/linux-bluetooth/CABBYNZ+CYMsDSPTxBn09Js3BcdC-x7vZFfyLJ3ppZGGwJKmUTw@mail.gmail.com/
Fixes: c70a7e4c

 ("Bluetooth: Add support for Not Connectable flag for Device Found events")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>