Basically, SD_BUF0 Tx/Rx addresses are same
in normal TMIO controller,
but, it is different on Renesas R-Car SDHI controller
if it uses DMAC
(Rx address needs to add 0x2000 to Tx address)

This patch adds new .dma_rx_offset and cares it
Tested-by: NNguyen Xuan Nui <nx-nui@jinso.co.jp>
Tested-by: NHiep Cao Minh <cm-hiep@jinso.co.jp>
Acked-by: NLaurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: NBen Dooks <ben-linux@fluff.org>
Signed-off-by: NKuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>