musb: sunxi: Make sunxi musb glue work without MUSB_PIO_ONLY

Now that it is possible to build in multiple dma engines, we can no longer
require MUSB_PIO_ONLY to be set when using the sunxi musb glue.

This patch adds dummy dma hooks to make the musb glue work without
MUSB_PIO_ONLY. This hooks are fake because we do not support dma with
musb on sunxi. The Allwinnner Android kernels have some dma code, but it
is disabled as Allwinner never managed to get it to work.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>