There is no reason to require the source arguments to be writeable so fix
this to allow constant source addresses.
Signed-off-by: NDavid Herrmann <dh.herrmann@gmail.com>
Acked-by: NMarcel Holtmann <marcel@holtmann.org>
Signed-off-by: NGustavo Padovan <gustavo.padovan@collabora.co.uk>