ext2: Adjust the comment of function ext2_alloc_branch

The name of argument is error in the header comment.
@num should be @indirect_blks.
At the same time, there was a lack of description of the two parameters
@blks and @goal.
This commit therefore fixes this header comment.
Signed-off-by: Shuning Zhang <sunny.s.zhang@oracle.com>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/ext2/inode.c

@@ -451,7 +451,9 @@ static int ext2_alloc_blocks(struct inode *inode,
 /**
  *	ext2_alloc_branch - allocate and set up a chain of blocks.
  *	@inode: owner
- *	@num: depth of the chain (number of blocks to allocate)
+ *	@indirect_blks: depth of the chain (number of blocks to allocate)
+ *	@blks: number of allocated direct blocks
+ *	@goal: preferred place for allocation
  *	@offsets: offsets (in the blocks) to store the pointers to next.
  *	@branch: place to store the chain in.
  *