Bluetooth: Introduce hci_dev_test_and_change_flag helper macro

Instead of manually coding test_and_change_bit on hdev->dev_flags all the
time, use hci_dev_test_and_change_flag helper macro.

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