Floss: Fix invalid handle detection in SCO connection complete hack

In pdl, the connection complete view only extracts 12 bits for the
connection handle, so even though some controller reports invalid handle
as 0xffff, the extracted value would be 0xfff.

This CL fixes the hack accordingly.

Bug: 294497459
Test: mma -j32
Test: build on ChromeOS
Tag: #floss
Change-Id: Ie0f56d51266ca80d8931203b766b734428fdf97a