fscrypt: shrink the size of struct fscrypt_inode_info slightly

Shrink the size of struct fscrypt_inode_info by 8 bytes by packing the
small fields into the 64 bits after ci_enc_key.

Link: https://lore.kernel.org/r/20240224060103.91037-1-ebiggers@kernel.org


Signed-off-by: Eric Biggers <ebiggers@google.com>