aidl: Change the way of convert string to integer link_id

hostapd_get_iface_by_link_id() need get correct link_id to check if
the hostapd_iface had added. Forcing the string link_id to an integer
type will result in the wrong link_id number causing hostapd to crash.
Change the way to convert string to integer link_id to get correct
link_id.

Bug: 340821197
Test: Start MLO SAP from UI.
Change-Id: I6a13a5d1837ae8565cccd08e6ce31c9f276b672f
1 file changed