vold: get the fscrypt kernel API declarations from linux/fs.h

bionic now has linux/fs.h from the 4.14 kernel, which has the fscrypt
kernel API declarations.  Replace the manual declarations in vold,
except for FS_AES_256_XTS_KEY_SIZE which is not available.

Test: built, booted device with f2fs encryption
Change-Id: I6a0e3117eaebe3baac7385421afce2169d46ad55
1 file changed