Bluetooth: fix passkey uninitialized when used

This patch fix the issue: warning:variable 'passkey' is uninitialized
when used here

Link: https://groups.google.com/forum/#!topic/clang-built-linux/kyRKCjRsGoU



Fixes: cee5f20f ("Bluetooth: secure bluetooth stack from bluedump attack")
Reported-by: kbuild test robot <lkp@intel.com>
Suggested-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Howard Chung <howardchung@google.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>