Bluetooth: Add confirm_hint parameter to user confirmation requests

When accepting a pairing request which fulfills the SSP auto-accept
criteria we need to push the request all the way to the user for
confirmation. This patch adds a new hint to the user_confirm_request
management event so user space can know when to show a numeric
comparison dialog and when to show a simple yes/no confirmation dialog.

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