mmc: core: Convert mmc_of_parse_voltage() to use device property API

mmc_of_parse() for a few years has been using device property API.
Convert mmc_of_parse_voltage() as well.

At the same time switch users to new API.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20210419112459.25241-2-andriy.shevchenko@linux.intel.com


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