f2fs: clean up lfs/adaptive mount option

This patch removes F2FS_MOUNT_ADAPTIVE and F2FS_MOUNT_LFS mount options,
and add F2FS_OPTION.fs_mode with below two status to indicate filesystem
mode.

enum {
	FS_MODE_ADAPTIVE,	/* use both lfs/ssr allocation */
	FS_MODE_LFS,		/* use lfs allocation only */
};

It can enhance code readability and fs mode's scalability.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/file.c

@@ -1126,7 +1126,7 @@ next_dnode:
 
 		if (!f2fs_is_checkpointed_data(sbi, *blkaddr)) {
 
-			if (test_opt(sbi, LFS)) {
+			if (f2fs_lfs_mode(sbi)) {
 				f2fs_put_dnode(&dn);
 				return -EOPNOTSUPP;
 			}