arm64: dts: amlogic: gxbb-odroidc2: remove UHS capability for SD card

arm64: dts: amlogic: gxbb-odroidc2: remove UHS capability for SD card

This is meant to resolve reboot not working on this board.

The problem is as follows. In order to be able to switch from HS to UHS
mode the bus voltage needs to be reduced from 3.3V down to 1.8V and this
is achieved by the "vqmmc-supply" regulator. The ROM bootloader is only
able to manage the card in HS mode (3.3V) and the switch HS->UHS happen
at boottime in the kernel. The problem appears when the reboot command
is issued or watchdog expires because in this case the "vqmmc-supply"
voltage is not returned back at 3.3V before rebooting the board so the
ROM bootloader will be completely stuck.

Therefore this commit removes all UHS modes which would cause
"vqmmc-summply" to switch from 3.3V to 1.8V.

In terms of performance the main drawback of this commit is limiting the
SD card bus speed to HS (25 MB/s) instead of UHS DDR50 (50 MB/s). However
this comes with the benefit of being able to reboot the board, so it
sounds like a reasonable compromise.

Reviewed-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Valerio Setti <vsetti@baylibre.com>
Link: https://lore.kernel.org/r/20250908-fix-reboot-v2-1-354d0e57c855@baylibre.com
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>