arm64: dts: imx8mm-kontron: Add support for ultra high speed modes on SD card

In order to use ultra high speed modes (UHS) on the SD card slot, we
add matching pinctrls and fix the voltage switching for LDO5 of the
PMIC, by providing the SD_VSEL pin as GPIO to the PMIC driver.

Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>