mmc: meson-gx: use new helpers mmc_regulator_enable/disable_vqmmc

Use new helpers mmc_regulator_enable/disable_vqmmc to simplify
the code.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Acked-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Link: https://lore.kernel.org/r/2ceb62da-07e6-bafc-c29e-13cc1cdde93a@gmail.com


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