Clean up safe_mode_config flag check in the functional code

This patch cleans up the flag check in the functional code. The
flag is already fully released in Android V

At the same time, the flag definition is not removed because it
is an exportable flag

Bug: 380326369
Bug: 276358140
Test: atest FrameworksVcnTests && atest CtsVcnTestCases
Flag: EXEMPT, clean up released flag
Change-Id: I985d37e192c4bc87ebd433f4de3b7fe93b039f7d