Reference DataSaver setting from BPF map on V+ only

Only reference DataSaverEnabled map on V+ platform because the
information in map before platform V is not time-precise. See comment in
this commit for detail.

Bug: 288340533
Test: presubmit
Change-Id: I0795e88e6006e6d24d27b63c31d0e3ed81d0262c
1 file changed