Bluetooth: MGMT: Fix not exposing debug UUID on MGMT_OP_READ_EXP_FEATURES_INFO

The debug UUID was only getting set if MGMT_OP_READ_EXP_FEATURES_INFO
was not called with a specific index which breaks the likes of
bluetoothd since it only invokes MGMT_OP_READ_EXP_FEATURES_INFO when an
adapter is plugged, so instead of depending hdev not to be set just
enable the UUID on any index like it was done with iso_sock_uuid.

Fixes: e625e50c ("Bluetooth: Introduce debug feature when dynamic debug is disabled")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>