ARM: dts: imx6qdl-kontron-samx6i: hook up DDC i2c bus

i2c2 is routed to the pins dedicated as DDC in the module standard.
Reduce clock rate to 100kHz to be in line with VESA standard and hook
this bus up to the HDMI node.

Fixes: 708ed264 ("ARM: dts: imx6qdl-kontron-samx6i: increase i2c-frequency")
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
[m.felsch@pengutronix.de: add fixes line]
Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>