dm: sunxi: Add pinmux functions which take a bank parameter

With driver model we will have access to a bank pointer, so we want to
use it rather than converting back to a number, and then back to a
bank pointer. Add functions to provide this feature.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>