dmaengine: stm32-dma: use bitfield helpers

Use the FIELD_{GET,PREP}() helpers, instead of defining custom macros
implementing the same operations.

Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Link: https://lore.kernel.org/r/20220829154646.29867-3-amelie.delaunay@foss.st.com


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