mmc: tmio,renesas_sdhi: move ssc_tappos to renesas_sdhi.h

struct tmio_mmc_host has "scc_tappos", but in fact, it is Renesas
private data.  Move it to renesas_sdhi.h

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>