Enable hardware based FBE on f2fs and adapt ext4 fs

Hardware File Based Encryption (FBE) uses crypto engine to
encrypt the user data with unique key for each file.
File name and data both are encrypted with this feature.
1. security/pfk: changes to support per file
   encryption for f2fs using hardware crypto engine.
2. fs/ext4: adapted crypto APIs for generic crypto layer.
3. fs/f2fs: support hardware crypto engine based per file
   encryption.
4. fs/crypto: export APIs to support hardware crypto
   engine based per file encryption.
Other changes made to provide support framework for per
file encryption.

Change-Id: I7981fa7f8f0c4bc058b80b7b8e342cfd81697c74
Signed-off-by: Neeraj Soni <neersoni@codeaurora.org>