powerpc/spufs: Fix incorrect buffer offset in regs write

We need to offset by *pos bytes, not *pos words.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/platforms/cell/spufs/file.c b/arch/powerpc/platforms/cell/spufs/file.c
index be0120d..d6a519e 100644
--- a/arch/powerpc/platforms/cell/spufs/file.c
+++ b/arch/powerpc/platforms/cell/spufs/file.c
@@ -578,7 +578,7 @@
 	if (ret)
 		return ret;
 
-	ret = copy_from_user(lscsa->gprs + *pos - size,
+	ret = copy_from_user((char *)lscsa->gprs + *pos - size,
 			     buffer, size) ? -EFAULT : size;
 
 	spu_release_saved(ctx);