sf: Defer DispSync initialization

Some DispSync members are initialized based on uninitialized static
members of sf, that are in turn initialized in sf constructor. Fix
the sequence by deferring DispSync initialization.

Current sequence:
sf constructor|-> DispSync constructor -> Access static sf members
              |-> Initialize sf static members

New sequence:
sf constructor|-> DispSync constructor
              |-> Initialize sf static members
              |-> DispSync init -> Access static sf members

Bug: 63671437
Test: "present fences are ignored" not present in SF dumpsys
Change-Id: I618d2bbbbd4e39fc382e67f85dd8d637dd82cf38