Bluetooth: Fix logic in hci_pin_code_request_evt

The mgmt_ev_pin_code_request event should not be sent to user space if
the request gets rejected by the kernel due to the pairable flag not
being set.

Signed-off-by: Johan Hedberg <johan.hedberg@nokia.com>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>