mmc: sdhci-s3c: Choose sdhci_ops based on variant

The difference between old S3C64xx and newer Exynos4 SDHCI controller
variants is in clock handling (the "no_divider" field in drvdata).
Choose the proper sdhci_ops based on the variant instead of patching
ops in probe, if Exynos4 is used.

This allows making struct sdhci_ops const for code safety and probably
opens further options in the future, as the dynamic pointer ops table is
not anymore that dynamic.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/20240414-mmc-const-sdhci-ops-v2-5-262f81faadac@kernel.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>