Bluetooth: Fix advertising duplicated flags

Bluetooth: Fix advertising duplicated flags

[ Upstream commit 6012b9346d8959194c239fd60a62dfec98d43048 ]

Instances may have flags set as part of its data in which case the code
should not attempt to add it again otherwise it can cause duplication:

< HCI Command: LE Set Extended Advertising Data (0x08|0x0037) plen 35
        Handle: 0x00
        Operation: Complete extended advertising data (0x03)
        Fragment preference: Minimize fragmentation (0x01)
        Data length: 0x06
        Flags: 0x04
          BR/EDR Not Supported
        Flags: 0x06
          LE General Discoverable Mode
          BR/EDR Not Supported

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>