dmaengine: sun6i: Move number of pchans/vchans/request to device struct

Preparatory patch: If the same compatible is used for different SoCs which
have a common register layout, but different number of channels, the
channel count can no longer be stored in the config. Store it in the
device structure instead.

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>