[CELL] spufs: fix array size of channel index

Based on a fix from Masato Noguchi <Masato.Noguchi@jp.sony.com>.

Remove the (incorrect) array size declarations in the spufs channel
arrays, and use ARRAY_SIZE rather than hardcoded values.

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