Bluetooth: Enhance error codes pair device command

If user space is trying to pair on not enabled transport
MGMT_STATUS_REJECT will be returned.

If user space is trying to pair on transport which controller does not
support, MGMT_STATUS_NOT_SUPPORTED will be returned.

Having separate error code for that scenario might be useful for
debugging at least.

Signed-off-by: Lukasz Rymanowski <lukasz.rymanowski@tieto.com>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>