[POWERPC] spufs: Remove spufs_dir_inode_operations

spufs_dir_inode_operations is exactly the same as
simple_dir_inode_operations.  Use that instead.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>