mmc: tmio: bus_shift become tmio_mmc_data member

.bus_shift is used to 16/32bit register access offset calculation on
tmio driver.  tmio_mmc_xxx is used from Toshiba/Renesas now, but this
bus_shift value depends on HW IP.  This patch moves .bus_shift to
tmio_mmc_data member and sets it on each driver.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Chris Ball <cjb@laptop.org>