mmc: sdhci-sprd: Constify struct sdhci_ops

The local struct sdhci_ops can be made const for code safety.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Link: https://lore.kernel.org/r/20240414-mmc-const-sdhci-ops-v2-3-262f81faadac@kernel.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>