Bluetooth: ssp: correct pairing failed callback

Current, the callback `pairing_complete` is called
when the pairing is filed. But there is a callback
`pairing_failed` for pairing failed case.

Correct the callback calling if pairing failed.
Call `pairing_failed` instead of `pairing_complete`
if the pairing failed.

Signed-off-by: Lyle Zhu <lyle.zhu@nxp.com>