mmc: sdhci-s3c: Provide documentation for missing struct properties

Describe properties; ext_cd_irq, clk_rates and no_divider (x2).

Squashes the following W=1 kernel build warnings:

 drivers/mmc/host/sdhci-s3c.c:126: warning: Function parameter or member 'ext_cd_irq' not described in 'sdhci_s3c'
 drivers/mmc/host/sdhci-s3c.c:126: warning: Function parameter or member 'clk_rates' not described in 'sdhci_s3c'
 drivers/mmc/host/sdhci-s3c.c:126: warning: Function parameter or member 'no_divider' not described in 'sdhci_s3c'
 drivers/mmc/host/sdhci-s3c.c:139: warning: Function parameter or member 'no_divider' not described in 'sdhci_s3c_drv_data'

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ben Dooks <ben-linux@fluff.org>
Cc: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
Link: https://lore.kernel.org/r/20200701124702.908713-5-lee.jones@linaro.orgSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/sdhci-s3c.c

@@ -107,8 +107,11 @@
  * @ioarea: The resource created when we claimed the IO area.
  * @pdata: The platform data for this controller.
  * @cur_clk: The index of the current bus clock.
+ * @ext_cd_irq: External card detect interrupt.
  * @clk_io: The clock for the internal bus interface.
+ * @clk_rates: Clock frequencies.
  * @clk_bus: The clocks that are available for the SD/MMC bus clock.
+ * @no_divider: No or non-standard internal clock divider.
  */
 struct sdhci_s3c {
 	struct sdhci_host	*host;
@@ -128,6 +131,7 @@ struct sdhci_s3c {
 /**
  * struct sdhci_s3c_driver_data - S3C SDHCI platform specific driver data
  * @sdhci_quirks: sdhci host specific quirks.
+ * @no_divider: no or non-standard internal clock divider.
  *
  * Specifies platform specific configuration of sdhci controller.
  * Note: A structure for driver specific platform data is used for future