dmaengine: jz4780: Set max number of SGs per burst

Total amount of SG list entries executed in a single burst is limited by
the number of available DMA descriptors.
This information is useful for device drivers utilizing this DMA engine.

Signed-off-by: Artur Rojek <contact@artur-rojek.eu>
Acked-by: Paul Cercueil <paul@crapouillou.net>
Link: https://lore.kernel.org/r/20210829195805.148964-1-contact@artur-rojek.eu


Signed-off-by: Vinod Koul <vkoul@kernel.org>