ARM: dts: imx6sx-udoo-neo: Fix reboot hang

After issuing a 'reboot' command the imx6sx-udoo-neo board does not
reboot as expected and it just hangs instead.

In mainline kernel only LDO enabled mode is supported. Do not provide
arm-supply/soc-supply nodes in the device tree, so that the board operates
in LDO enabled mode and can then successfully reboot via watchdog.

Fixes: 76e691fc ("ARM: dts: imx6sx: Add UDOO Neo support")
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Tested-by: Breno Lima <breno.lima@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>