mmc: core: Prepare mmc_send_cxd_data() to be re-used for additional cmds

The function mmc_send_cxd_data() sends a data read command of ADTC type and
prepares to receive an R1 response. To make it even more re-usable, let's
extend it with another in-parameter for the command argument. While at it,
let's also rename the function to mmc_send_adtc_data() as it better
describes its purpose.

Note that, this change doesn't add any new users of the function. Instead
that is done from subsequent changes.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com>
Acked-by: Avri Altman <avri.altman@wdc.com>
Link: https://lore.kernel.org/r/20210504161222.101536-7-ulf.hansson@linaro.org