Merge below two conditions into f2fs_may_encrypt() for cleanup
- IS_ENCRYPTED()
- DUMMY_ENCRYPTION_ENABLED()

Check IS_ENCRYPTED(inode) condition in f2fs_init_inode_metadata()
is enough since we have already set encrypt flag in f2fs_new_inode().
Signed-off-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>