dmaengine: stm32-dma: use dma_set_max_seg_size to set the sg limit

This patch adds dma_set_max_seg_size to define sg dma constraint.
This constraint may be taken into account by client to scatter/gather
its buffer.

Signed-off-by: Ludovic Barre <ludovic.barre@st.com>
Signed-off-by: Amelie Delaunay <amelie.delaunay@st.com>
Link: https://lore.kernel.org/r/20200129153628.29329-6-amelie.delaunay@st.com


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