Bluetooth: AMP: Mark controller radio powered down after HCIDEVDOWN

After getting HCIDEVDOWN controller did not mark itself as 0x00 which
means: "The Controller radio is available but is currently physically
powered down". The result was even if the hdev was down we return
in controller list value 0x01 "status 0x01 (Bluetooth only)".

Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>