arm: dts: verdin-am62: use gpio-hog for sleep moci

arm: dts: verdin-am62: use gpio-hog for sleep moci

In Linux, we allow sleep moci to be turned off when the carrier board
supports it and the system is in suspend. In U-Boot, however, we want
the sleep moci to be always on. So we use a gpio hog and disable the
regulator. This change is necessary because we switched to upstream
device tree files with commit c07bba7a2c7e ("verdin-am62: move verdin
am62 to OF_UPSTREAM"). A recent upstream patch removes the gpio hog from
the Linux device tree, so we need to add it to the u-boot dtsi. The
following patch will remove the gpio hog from the Linux device tree:
https://lore.kernel.org/linux-devicetree/20240301084901.16656-1-eichest@gmail.com/
The U-Boot patch can be applied without it and will not break the build.

Signed-off-by: Stefan Eichenberger <stefan.eichenberger@toradex.com>