AFS: write back dirty data on unmount

Fix AFS to write back dirty on unmounting.  This didn't happen because
afs_super_ops.drop_inode was pointing to generic_delete_inode.  Now this
pointer is left set to NULL so that the default behaviour occurs instead.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/afs/super.c

@@ -47,7 +47,6 @@ struct file_system_type afs_fs_type = {
 static const struct super_operations afs_super_ops = {
 	.statfs		= afs_statfs,
 	.alloc_inode	= afs_alloc_inode,
-	.drop_inode	= generic_delete_inode,
 	.write_inode	= afs_write_inode,
 	.destroy_inode	= afs_destroy_inode,
 	.clear_inode	= afs_clear_inode,