[ARM] Feroceon: small cleanups to L2 cache code

- Make sure that coprocessor instructions for range ops are contiguous
  and not reordered.

- s/invalidate_and_disable_dcache/flush_and_disable_dcache/

- Don't re-enable I/D caches if they were not enabled initially.

- Change some masks to shifts for better generated code.

Signed-off-by: Nicolas Pitre <nico@marvell.com>
Acked-by: Lennert Buytenhek <buytenh@marvell.com>