mmc: dw_mmc: Reset DMA before enabling IDMAC

mmc: dw_mmc: Reset DMA before enabling IDMAC

We've already got a reset of DMA after it's done.  Add one before we
start DMA too.  This fixes a data corruption on Rockchip SoCs which
will get bad data when doing a DMA transfer after doing a PIO transfer.

We tested this on an Exynos 5800 with HS200 and didn't notice any
difference in sequential read throughput.

Signed-off-by: Sonny Rao <[email protected]>
Signed-off-by: Doug Anderson <[email protected]>
Tested-by: Doug Anderson <[email protected]>
Acked-by: Jaehoon Chung <[email protected]>
Tested-by: Jaehoon Chung <[email protected]>
Reviewed-by: Alim Akhtar <[email protected]>
Signed-off-by: Ulf Hansson <[email protected]>