docs: filesystems: vfs: Use uniform spacing around headings

Currently spacing before and after headings is non-uniform.  Use two
blank lines before a heading and one after the heading.

Use uniform spacing around headings.
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Tobin C. Harding <tobin@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/filesystems/vfs.txt

@@ -319,6 +319,7 @@ Whoever sets up the inode is responsible for filling in the "i_op"
 field.  This is a pointer to a "struct inode_operations" which describes
 the methods that can be performed on individual inodes.
 
+
 struct xattr_handlers
 ---------------------
 
@@ -511,6 +512,7 @@ otherwise noted.
   tmpfile: called in the end of O_TMPFILE open().  Optional, equivalent to
 	atomically creating, opening and unlinking a file in given directory.
 
+
 The Address Space Object
 ========================
 
@@ -584,8 +586,10 @@ and the constraints under which it is being done.  It is also used to
 return information back to the caller about the result of a writepage or
 writepages request.
 
+
 Handling errors during writeback
 --------------------------------
+
 Most applications that do buffered I/O will periodically call a file
 synchronization call (fsync, fdatasync, msync or sync_file_range) to
 ensure that data written has made it to the backing store.  When there
@@ -616,6 +620,7 @@ file->fsync operation, they should call file_check_and_advance_wb_err to
 ensure that the struct file's error cursor has advanced to the correct
 point in the stream of errors emitted by the backing device(s).
 
+
 struct address_space_operations
 -------------------------------
 
@@ -1207,9 +1212,11 @@ manipulate dentries:
 	and the dentry is returned.  The caller must use dput()
 	to free the dentry when it finishes using it.
 
+
 Mount Options
 =============
 
+
 Parsing options
 ---------------
 
@@ -1224,6 +1231,7 @@ The <linux/parser.h> header defines an API that helps parse these
 options.  There are plenty of examples on how to use it in existing
 filesystems.
 
+
 Showing options
 ---------------
 
@@ -1245,6 +1253,7 @@ The underlying reason for the above rules is to make sure, that a mount
 can be accurately replicated (e.g. umounting and mounting again) based
 on the information found in /proc/mounts.
 
+
 Resources
 =========