f2fs: verify file type early in f2fs_fallocate

This patch changes to verify file type early in f2fs_fallocate for
cleanup, meanwhile this also fixes to add missing verification for
expand_inode_data.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>