fs/erofs: add erofs filesystem support

This patch mainly deals with uncompressed files.

Signed-off-by: Huang Jianan <jnhuang95@gmail.com>
diff --git a/include/fs.h b/include/fs.h
index c8df388..b607b00 100644
--- a/include/fs.h
+++ b/include/fs.h
@@ -17,6 +17,7 @@
 #define FS_TYPE_UBIFS	4
 #define FS_TYPE_BTRFS	5
 #define FS_TYPE_SQUASHFS 6
+#define FS_TYPE_EROFS   7
 
 struct blk_desc;