rockchip: rk3399-nanopi-4: Allow MMC driver to control SD regulators

rockchip: rk3399-nanopi-4: Allow MMC driver to control SD regulators

This change removes the "regulator-always-on" property from the
"vcc3v0_sd" (vmmc-supply) and "vcc_sdio" (vqmmc-supply) regulators,
which otherwise prevents the MMC driver from being able to power cycle
the SD card as part of the initialization procedure.

It also removes the "regulator-boot-on" from the "vcc_sdio" regulator,
which could theoretically damage a SD card that is already initialized
in a low voltage mode.

Signed-off-by: Justin Klaassen <justin@tidylabs.net>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>