mmc: core: Add missing documetation for 'mmc' and 'ios'

Remainder of the kerneldoc descriptions look present and correct.

Fixes the following W=1 kernel build warnings:

 drivers/mmc/core/regulator.c:178: warning: Function parameter or member 'mmc' not described in 'mmc_regulator_set_vqmmc'
 drivers/mmc/core/regulator.c:178: warning: Function parameter or member 'ios' not described in 'mmc_regulator_set_vqmmc'
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20200701124702.908713-4-lee.jones@linaro.orgSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/core/regulator.c

@@ -159,6 +159,8 @@ static int mmc_regulator_set_voltage_if_supported(struct regulator *regulator,
 
 /**
  * mmc_regulator_set_vqmmc - Set VQMMC as per the ios
+ * @mmc: the host to regulate
+ * @ios: io bus settings
  *
  * For 3.3V signaling, we try to match VQMMC to VMMC as closely as possible.
  * That will match the behavior of old boards where VQMMC and VMMC were supplied