mmc: tmio: tmio_mmc_data has .dma_rx_offset

Current .dma_rx_offset is implemented under tmio_mmc_dma.
It goes to tmio_mmc_data by this patch.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>