[POWERPC] Sky Cpu and Nexus: use seq_file/single_open on proc interface

This patch changes proc interface to be used with single_file/seq_open
calls.

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>