Bluetooth: Disable Extended Adv if enabled

Disabling LEGACY_ADV when EXT_ADV is enabled causes
'command disallowed' during DIRECTED_ADV. This Patch fixes this
issue.

Signed-off-by: Sathish Narsimman <sathish.narasimman@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>