arm64: dts: imx8mm-kontron: Add Sitronix touch controller in DL devicetree

arm64: dts: imx8mm-kontron: Add Sitronix touch controller in DL devicetree

Some new panels have the Sitronix touch instead of Goodix. Support them
by adding a node for the new controller. The bootloader needs to detect
the correct controller and enable/disable the nodes accordingly. To make
this easier add labels for both nodes.

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