spi, serial: move to dma_transfer_direction

fixup usage of dma direction by introducing dma_transfer_direction,
this patch moves spi, serial drivers to use new enum

Signed-off-by: Vinod Koul <[email protected]>
Cc: Grant Likely <[email protected]>
Cc: Alan Cox <[email protected]>
Acked-by: Mika Westerberg <[email protected]>
7 files changed