powerpc/cell/spufs: Fix status attribute permission

We are registering the attribute with permission 0644 but it
doesn't have a store callback, which causes WARN_ON's during
boot. Fix the permission.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/platforms/cell/spu_base.c

@@ -715,7 +715,7 @@ static ssize_t spu_stat_show(struct device *dev,
 		spu->stats.libassist);
 }
 
-static DEVICE_ATTR(stat, 0644, spu_stat_show, NULL);
+static DEVICE_ATTR(stat, 0444, spu_stat_show, NULL);
 
 #ifdef CONFIG_KEXEC