fs: fix writeback.c kernel-doc warnings

Fix kernel-doc warnings in fs/fs-writeback.c by moving a #define macro
to after the function's opening brace. Also #undef this macro at the
end of the function.

..//fs/fs-writeback.c:1984: warning: Excess function parameter 'inode' description in 'I_DIRTY_INODE'
..//fs/fs-writeback.c:1984: warning: Excess function parameter 'flags' description in 'I_DIRTY_INODE'
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/fs-writeback.c

@@ -1981,9 +1981,9 @@ static noinline void block_dump___mark_inode_dirty(struct inode *inode)
  * page->mapping->host, so the page-dirtying time is recorded in the internal
  * blockdev inode.
  */
-#define I_DIRTY_INODE (I_DIRTY_SYNC | I_DIRTY_DATASYNC)
 void __mark_inode_dirty(struct inode *inode, int flags)
 {
+#define I_DIRTY_INODE (I_DIRTY_SYNC | I_DIRTY_DATASYNC)
 	struct super_block *sb = inode->i_sb;
 	int dirtytime;
 
@@ -2093,6 +2093,7 @@ void __mark_inode_dirty(struct inode *inode, int flags)
 out_unlock_inode:
 	spin_unlock(&inode->i_lock);
 
+#undef I_DIRTY_INODE
 }
 EXPORT_SYMBOL(__mark_inode_dirty);