mmc: sdhci: Remove unused prototype declaration in the header

sdhci_card_detect() is not defined anywhere. Remove it.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/20211014132613.27861-3-andriy.shevchenko@linux.intel.com


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