mmc: mmci: stm32: prepare other delay block support

Create an sdmmc_tuning_ops struct to ease support for another
delay block peripheral.

Signed-off-by: Yann Gautier <yann.gautier@foss.st.com>
Link: https://lore.kernel.org/r/20230619115120.64474-6-yann.gautier@foss.st.com


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>