Now that emulated FBE is no longer supported, there is no longer any
distinction between native FBE and emulated FBE. There is just FBE.
Referring to FBE as "fscrypt" is also poor practice, as fscrypt (the
Linux kernel support for filesystem-level encryption) is just one part
of FBE, the Android feature.
Therefore, rename fscrypt_is_native() to IsFbeEnabled().
Bug: 232458753
Change-Id: Idf4cb25d37bc3e81836fcc5a1d96f79ccfa443b7
a6957c0f7a