ARM: dts: mmp3-dell-ariel: Enable the HSIC

There's a SMSC USB2640 (USB hub & SD controller) connected to it, but
the SD card slot footprint is unpopulated. Also connected to the hub is
a SMSC LAN7500 gigabit ethernet adapter.

Link: https://lore.kernel.org/r/20191220065314.237624-6-lkundrak@v3.sk


Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Signed-off-by: Olof Johansson <olof@lixom.net>