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

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 <[email protected]>
Cc: Ben Dooks <[email protected]>
Cc: Jaehoon Chung <[email protected]>
Signed-off-by: Lee Jones <[email protected]>
Reviewed-by: Jaehoon Chung <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Ulf Hansson <[email protected]>