Flag guard to make fsverity_init a no-op

As early as fsverity_init, the flag can only be static (thus
is_fixed_read_only). It is now a constant/false and will be flipped
during the ramp up at build time.

Bug: 290064770
Test: mma
Test: Inspect the generated code
Change-Id: I4bd1addb996705f6e6b9f75313bf22b9ecd3e11c
3 files changed