ARM: dts: rockchip: rk3288-vyasa: Use vmmc-supply from PMIC

rk808, SWITCH_REG1 has configured for sdmmc regulator as vcc_sd,
so use the same by renaming vcc33_sd to vcc_sd(as per schematic)
and drop explicit regulator definition from root.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>