[PATCH] spufs: clear dsisr on CLASS1[Mf] exception

Because of always clearing DSISR at spu class 1 interrupt handler,
kernel may lose Class1[Mf] interrupt.

Signed-off-by: Masato Noguchi <Masato.Noguchi@jp.sony.com>
Signed-off-by: Geoff Levand <geoff.levand@am.sony.com>
Signed-off-by: Arnd Bergmann <arndb@de.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>