[MAC Randomization] Removed feature flag to align framework global flag

Removed feature flag and change to check global flag as framework MAC
randomization api does.

Bug: 127817791
Bug: 120743100
Test: atest WifiPrivacyPreferenceControllerTest
Change-Id: Iefe0d442326ca6a9461af8724a1632fd238d8d2b
1 file changed