mmc: sdhci: replace mmc->parent with mmc_dev() for consistency

mmc: sdhci: replace mmc->parent with mmc_dev() for consistency

As pointed out by Ulf, "both "mmc->parent" and mmc_dev(mmc) are being
used in the entire c-file". Convert all the mmc->parent usage in all
sdhci host driver to mmc_dev() for consistency.

Suggested-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Link: https://lore.kernel.org/r/20210324155013.1e5faa3c@xhacker.debian
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>